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How to parse String to LocalDate in Java 8 - DateTimeFormatter Example

From Java 8 onward, you are no longer dependent on the buggy and bulky SimpleDateFormat class to parse and format date Strings into real Date object in Java e.g. java.util.Date. You can use the DateTimeFormatter class from java.time package for all your formatting and parsing need. You are also no longer required to use another buggy class java.util.Date if you are doing fresh development, but if you have to support legacy code then you can also easily convert LocalDate and LocalTime to java.util.Date or java.sql.Date. In this tutorial, we will learn about both parsing String to date in Java and formatting Date into String.

10 Free Java 8 Certification Sample Questions - OCAJP8 and OCPJP8 - 1Z0-808 and 1Z09 dumps

If you are preparing for Oracle Java SE 8 Certifications e.g. OCAJP8 and OCJP8, also known as exam 1Z0-808 and 1Z0-809 and looking for some free practice tests then you have come to the right place. In this article, I am going to share some of the best OCAJP 8 and OCPJP 8 mock tests available for free of cost online, so that you can check your speed and accuracy before the real exam. These tests are not just useful for Oracle's Java OCA and OCP certification but also for upgrade exams like OCJP 8 upgrade exams with code 1Z0-810 and 1Z0-813, upgrade to Java SE 8 from Java 6 and prior version. Many of these practice tests are like web simulator where you need to solve a relatively small number of questions within 45 to 60 minutes. The web simulator also includes timer so that you can finish these free mock tests on time.

How to convert Integer to String in Java - Example

This is the second part of String to Integer data type conversion tutorial in Java, in the first part you have learned how to convert String to Integer and in this article, you will learn the opposite i.e. convert from Integer to String. Actually, you can apply all the tricks, which I had told you before about converting long to String, and autoboxing will take care of converting int to Integer in Java. But, if you care for performance and believe in not using auto-boxing when not needed then there are still a couple of ways which directly converts an Integer object to String e.g. Integer.toString() method, which returns a String object and doesn't have any auto-boxing overhead. Let's see a couple of more ways to convert an Integer to String in Java.

10 Books Java Developers Should Read in 2019 - Best Of Lot

Hello guys, If you are Java developer and wondering what to read in 2019 then you have come to the right place. In this article, I am going to share 10 books on Java, Spring, and related technology a Java developer can read. I have included books for both experienced Java developer who is more inclined to learn about architecture stuff,  developing for Cloud, MicroService, Java 9, and Spring 5 features and thinking of learning Kotlin to improve their productivity, but I have not forgotten to junior and less experienced Java developers or some who are thinking to start their journey into Java world in 2019.

10 Tools Java Developers Should Learn in 2019

We are just a week away to 2019 and many programmers have already started making a good process to their goals for 2019, which is very good, but if you are someone, who is still not sure what to learn in 2019 then you have come to the right place. In past, I have shared 10 things Java developers to learn in 2019 and last week I published top 5 Java Frameworks to learn, but there is one topic which kept coming from my readers.  The question which I have received this week a couple of times form my fellow Java developers and readers is which tools Java programmers should learn in 2019? or what are some good Java tools used in application development? and finally, what should I learn in 2019? I have been answering this question by writing blog posts e.g. 10 Testing Tools Java developers should learn in 2019 and in this article, I am going to share some of the best Java tools you can learn in 2019.

10 High Paying Technologies Programmers Can Learn in 2019

Since last a couple of the week, I have been doing some research about what to learn in 2019 when I stumbled about StackOverflow's Developer Survey for 2017. It's one of the best surveys for software developers, which provides useful insights about programming and IT world. One of the things I really like about this survey was its several lists e.g. the list of top 10 programming languages and the most loved frameworks by programmers, but the one I found most useful was the list of top paying technologies. This is a great list and allow you to choose what you can learn in 2019 to go to the next level in your career in terms of both financial and career growth.

5 Things You can Gift to Programmers,Software Developers and Tech Geeks

So, its that time of the year again when you start thinking about gifts for your programmer boyfriend, husband, colleagues or your near dear ones. Even if selecting gifts were not tough, if your friend happened to be a programmer, it becomes slightly tougher. You might have heard that Programmers are aloof, nerd and tech freaks, well, you heard it right. Programmers  prefers to be alone in their own world but they also like gifts and you got it right, they are a nerd so they like books, gadgets, music and something which help them to learn something e.g. a PluralSight membership.

In 2017, gadgets like Apple Watch and Samsung Gear is rocking but that's what everyone is buying so if you want to be a little bit different, chose the one from this list.

5 Free Linux Courses for Programmers and IT Professionals to Learn Online

Linux is one of the most popular operating systems to run server-side applications. I have seen almost all Java applications running on Linux barring a couple of them which runs on Windows as service. If you take out standalone apps like IDEs or tools, most of the real world Java applications run on Linux e.g. payment gateways, trading systems, and other financial applications. That's why it's very important for any programmer, IT professional, or a developer to learn and understand Linux, both operating system, as well as command line.

3 Books to learn Java Programming from Scratch in 2019 - Best of Lot Must Read

I receive half a dozen emails every day asking about which is the best to learn Java from scratch? Which book should I read in 2019 to learn Java? or Which is the best Java for beginners? When I receive such email, before giving my recommendation I ask two questions, first do you have any programming experience? e.g. Are you coming from C, C++ or Python background? Or you are a fresher with no experience in programming, just a couple of classes on data structure and algorithm and operating system on college. If the guy some prior experience I recommend him the book like Core Java for the Impatient which teaches basics of Java programming language and API and also how to use Java in right way.

Top 10 Programming Languages to Learn in 2019 - (Java, Python, and JavaScript)

Hello guys, 2018 is coming to end and 2019 is approaching fast. This is the time, most of us start making our goals e.g. physical goals, educational goals, and financial goals. As a programmer, one of our goals is to learn new technologies and programming languages, but which languages should you learn? Since learning a programming language requires both time and patience, you should learn a language which is worth the effort i.e. it can reward you a better job and career growth. In this article, I am going to share with you the top 10 programming languages you can learn for 2019.

Top 5 Amazing Gifts for Programmers, Coders, and Software Developers

If you are planning for a surprise gift to your programmer boyfriend and husband on this holiday season e.g. Black Friday, on Christmas, or New Year or maybe on his next birthday, but not sure what to gift, then you have come to the right place. In this article, I am going to share some of the best gifts every programmer wish for. To be honest with you, buying a gift is easy but finding the right gift is very tough. I have spent countless hours on the internet to find a perfect gift for one of my colleague's husband and this article is a result of that research. The general perception of programmers is that they are a nerd, they love books, gadgets, cool stuff, music, but the perfect gift is something which not only provides the enjoyment but also the value.

Java 8 compute() and computeIfPresent() Example

The JDK 8 has added several useful methods in existing interfaces e.g. java.util.Map, java.util.Collection, and java.util.concurrent.ConcurrentMap. Thanks to default methods, the much-needed evolution of existing interfaces become possible. Out of many useful methods, one method which stands out to me is the compute() method, which allows you to update a value in ConcurrentHashMap atomically. As per Java documentation, The compute() function tries to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). The entire function is performed atomically.

10 ways to learn a New Technology, Programming language, Frameworks, or Libraries in 2019

One of the main challenges of being a programmer or software engineer is the constant learning. Yes, that's true. As a programmer or developer, we always need to learn new things, sometimes every year. Thanks to C, Java, Linux, and SQL, we still have some ground but the way these technologies are used changes every year. For example, we have a new JDK 9 release in 2017, even though many Java developers are still learning Java 8. We also have a Spring Framework 5.0 release in 2017, combined with Spring Security 5.0 and Spring Boot 2.0 release, which many of us need to learn in 2018.

10 Examples of Collectors and Stream in Java 8

As the name suggests, Collectors class is used to collect elements of a Stream into Collection. It acts as a bridge between Stream and Collection and you can use it to convert a Stream into different types of Collections e.g. List, Set, Map. Btw, it not just limited to that, it even provides functionalities to join String, group by, partition by and several other reduction operators to return a meaningful result. It's often used along with collect() method of Stream class which accepts a Collectors. In this article, we'll learn Collectors by following some hands-on examples.

Top 5 Spring Cloud Annotations for Java Developers

If you are developing Java application for Cloud then you should learn Spring Cloud, a great framework and extension of popular Spring framework which can help you to develop a cloud-native Java application. Spring Cloud provides several necessary services required for a cloud-based Java application like configuration management, service discovery, circuit breakers, intelligent routing, micro-proxy, a control bus, one-time tokens, global locks, leadership election, distributed sessions, cluster state etc. On top of that, it builds on the Spring framework so it automatically provides the essential features like dependency injection and inversion of control, which results in loosely coupled and easy to test Java application.

How to Rotate an Array to Left and Right by a given Number in Java? - Coding Program with Solution

Hello guys, welcome to this post with another array based coding problem. In the last article, we've learned about finding missing numbers in the array with duplicates and today we'll solve the problem of rotating an array by left or right by given number. For example, suppose an integer array {1, 2, 3} is given and it was asked to rate this array to the left by 3 then the result array will look like {2, 3, 1} because it was rotated twice on left. Similarly if asked to rotate the same array twice by right then we'll get {1, 2, 3}, the same array is back. This is an interesting problem and it's quite easy to solve but I have many programmers struggles with this one as well. So, a little bit of practice and learning will not hurt.

Top 5 Free Courses to Learn Web Development in 2019 - Best of Lot

Hello guys, I have been sharing a lot of free online courses and books on various technology and programming language e.g, Python, Java, C++, JavaScript, PHPReact, Angular, Spring in this blog from quite some time and today I have brought some great free courses to learn basics of web development. Web Development is an important skill for programmers in this era of Startups. As a programmer or software developer, you should know how to create a website and how to create a mobile app of your own. Though it's not easy. Coding is like art and many people born with coding sense, I mean they love coding, they love to create stuff e.g. websites, mobile apps, games etc and they love to automate things. They are a very good self-learner and almost learn anything by themselves, but don't get discouraged if you don't have those skills. By perseverance and hard work, you can also learn whatever you want. In the past, I have shared some tips to learn a new technology and books and courses are an integral part of it.

How to Send HTTP Request from Java Program - Example Tutorial

If you are thinking is it possible to send an HTTP request from a Java program and if yes, how to send a simple HTTP GET request in Java, then you have come to the right place. In this article, I'll show you how you can use the HttpURLConnection class from java.net package to send a simple HTTP request in Java. But, first let me answer your first question, is it possible to send HTTP request in Java? Yes, it's possible and you can send any kind of HTTP request e.g. GET, POST, PUT, DELETE, HEAD, or PATCH. The java.net package provides a class called HttpURLConnection, which can be used to send any kind of HTTP or HTTPS request from Java program.

100+ Data Structure and Algorithm Interview Questions Answers for Programmers

Data structure and algorithms are core part of any Programming job interview. It doesn't matter whether you are a C++ developer, a Java developer or a Web developer working in JavaScript, Angular, React, or Query. As a computer science graduate, its expected from a programmer to have strong knowledge of both basic data structures e.g. array, linked list, binary tree, hash table, stack, queue and advanced data structures like the binary heap, trie, self-balanced tree, circular buffer etc. I have taken a lot of Java interviews for both junior and senior positions in the past, and I have been also involved in interviewing C++ developer. One difference which I have clearly noticed between a C++ and a Java developer is their understanding and command of Data structure and algorithms.

5 Free Servlet, JSP, and JDBC Online Courses for Advanced Java Developers

If you are a Java developer working on a Java JEE projects e.g. Java web application or you want to get into that by learning server-side technologies like Servlet, JSP, and JDBC then you have come to the right place. In this article, I will share some free online courses to learn Servlet, JSP, and JDBC at your own pace. If you want to become a rockstar Java web developer then you must have a good understanding of these basic web technologies before you learn frameworks like Spring and Hibernate. These frameworks work on top of these basic technologies and if you don't know them then you would often struggle to debug and troubleshoot problems in real world.

How to Set Specific Java Version for Maven in Windows?

Maven is a great build tool and most of the Java developer uses Maven to build their projects, but like any other tool, there are some intricacies which you need to know while using it. One of them is that Maven uses Java version from the JAVA_HOME environment variable and not the PATH environment variable. If you have multiple JDK installed on your machine and getting an Unsupported major.minor version 51.0 or Unsupported major.minor version 52.0 error while building your project but have right Java version in PATH then you may need to check the JAVA_HOME and update it. If you don't have access to do it then you can still change JAVA_HOME using set command in your local shell and run the Maven's mvn command to build the project

Why you should not use SELECT * in SQL Query

I have read many articles on the internet where people suggest that using SELECT * in SQL query is a bad practice and you should always avoid that. Instead, you should always use an explicit list of columns. That's a good suggestion and one of the SQL best practice I teach to junior developers, but many of them don't explain the reason behind it.  Unless you explain some reasons why one should not use SELECT * in queries, it's difficult to convince many SQL developers,  many of whom have started learning SQL by doing SELECT * from EMP in Oracle database. In this article, I will try to bridge that gap by giving some practical reasons of why using SELECT * in Query is not a good idea.

Top 5 Free Angular Courses for Web Developers to Learn Online

Angular is one of the most popular JavaScript frameworks for creating web apps. It helps you in creating complex web applications in less time. It's maintained by Google so you can also rest assured that this powerhouse of a framework is built with speed and purpose and here for a long run.  Angular is also the most popular framework in the world for building single page applications.  The framework was first launched as Angular JS which allowed building a web application using Model View Controller concept and it was hugely popular but it was later re-written completely, which is now known as simply Angular or Angular 2. Even though many web developers use Angular and Angular JS interchangeably they are very different and don't share anything expect Angular in their Name.

Top 20 System Design Interview Questions for Java Programmers

System design questions are an important part of programming job interviews and if you want to do well, you must prepare this topic. In the past, when I shared my list of programming interview questions, I have shared a couple of System design questions but my readers kept asking me for more questions, as it is a hard topic to master and more and more practice is needed. I had my own list of questions which I have collected from various interviews with friends and colleagues but I needed more questions for this article and my own preparation then I stumbled upon Grokking System Design Interview course. It's an excellent resource because it not only gives you a lot of System design question but also provide all the knowledge and tools you need to solve those questions.

5 Difference between BufferedReader and Scanner class in Java - File Tutorial Example

Hello guys, welcome to my blog. Today, we'll discuss another interesting Java interview questions, BufferedReader vs Scanner. It's not only important from interview point of view but also to work efficiently with Java. Even though both BufferedReader and Scanner can read a file or user input from the command prompt in Java, there some significant differences between them. One of the main difference between BufferedReader and Scanner class is that former class is meant to just read String or text data while Scanner class is meant to both read and parse text data into Java primitive types like int, short, float, double, and long.

Top 5 Free Spring Core Professional Certification Mock Exams and Practice Questions

Many Java developers don't know that similar to Oracle's Java certification, there is also a Spring certification program, which certifies yourself for your Spring framework skill. There are three Spring certifications currently available, Spring Professional certification exam, which certifies on your general knowledge about Spring framework, Spring Web Application Developer exam, which certifies you about your Spring MVC skill and Spring Enterprise Integration Specialist certification exam, which is for advanced Spring Integration skill. Earlier, SpringSource provides these certifications but now they are provided by Pivotal, the company behind the Spring framework.

Difference between final vs finally and finalize in Java? Answer

The final, finally, and finalize are one of the three confusing keywords, modifiers and methods in Java. They sound similar but they are for different purpose. For example, the final keyword is a modifier in Java. When you use the final keyword with a class it becomes a final class and no one can extend this e.g. String is final in Java. When you use the final modifier with method than it cannot be overridden in a subclass, and when you use the final keyword with a variable, it becomes a constant i.e. its value cannot be changed once assigned. On the other hand, finally is a keyword related to exception handling in Java. It's often used with try block and it's part of try, catch and finally trio.

How to add/remove new elements to an array in Java?

Java beginners often ask how to add new elements to an array? or how to remove elements from an array in Java? is that possible in Java? Well, no, it's not possible in Java because arrays length cannot be changed once created. Which means neither you can add new elements nor you can remove an old one. All you can do is that reassign values to the different bucket. For example, if you have a String array of length 3 e.g. {"java", "is", "great"} then you can just replace the individual index to make it like {"Python", "is", "great"} by replace "java" with "Python" at first index, but you cannot add or remove elements.

How to Print all leaf Nodes of a Binary tree in Java - Coding Interview Questions

This is another interesting coding problem which is based on a binary tree and mostly asked beginner programmers. If you have some experience in solving binary tree based problems then it's rather easy to solve because, like many other binary tree algorithms, you can use recursion to print all leaf nodes of a binary tree in Java. Since the tree is a recursive data structure, you can apply the same algorithm to both the left and right subtree. In order to solve this problem, the first thing you should know is what is a leaf node because if you don't know that then you won't be able to solve the problem. Well, a leaf node is the one who's left and right child nodes are null.

How to Reverse a String in place in Java - Example

One of the common Java coding interview questions is to write a program to reverse a String in place in Java, without using additional memory. You cannot use any library classes or methods like e.g. StringBuilder to solve this problem. This restriction is placed because StringBuilder and StringBuffer class define a reverse() method which can easily reverse the given String. Since the main objective of this question is to test the programming skill and coding logic of candidate, there is no point giving him the option to use the library method which can make this question trivial. Now, how do you solve this problem? If you are familiar with array data structure then it would be easy for you. Since String is backed by a character array, you can use the same in place algorithm we have used to reverse an array in place.

How to use ConcurrentHashSet from ConcurrentHashMap in Java 8 - Example Tutorial

There is no ConcurrentHashSet in JDK 8 but you can still create one for yourself by using the ConcurrentHashMap class of java.util.concurrent package. There is a new method added into ConcurrentHashMap in JDK 8, newKeySet(), which allows you to create a concurrent hash set backed by a concurrent hash map. If you remember whenever you get keys from the map they are returned in a Set e.g. for the old keySet() method because map only has unique keys. Since map doesn't allow duplicate keys, it can be used as a set, as long as you only care for keys or just one element. That's why Java designers are added newKeySet() method to convert a map to set. This is also a static method, which means you don't need a ConcurrentHashMap object to create a concurrent hash set.

Top 10 Spring Framework Annotations for Java Developers

There is no doubt that Spring framework is one of the most popular Java frameworks and it has made the life of Java developer easy by providing some awesome features in the last 15 years. Spring uses dependency injection to configure and bind your application together but it doesn't force you to implement one of its interfaces. This allows you to code POJO (plain old Java objects), a class with methods and attributes to do most of your stuff. Then the questions come, how do Spring provides those magical features if it doesn't ask you to implement their interface, well they use annotations and many of them. You will find some of the most common annotations in this article, which is must for a Java developer to work with Spring.

5 Free Database and SQL Query Courses for Programmers to Learn Online

Hello guys, I have been sharing some free programming resources e.g. books and courses in this blog for quite some time. Earlier I have shared free courses on Java, Maven, Spring, and Data Structure and Algorithms and today I'll share some of the free online training courses to learn SQL and Database. Why you should learn SQL? Well, it's one of the must-have skill for programmers, application developer, and IT professionals. Like Linux, this is one skill which is going to serve you longer than any other programming language, framework, or library.

3 Examples to Generate Random Integers on a Range in Java

Manytimes you need to generate random numbers, particular integers in a range but unfortunately, JDK doesn't provide a simple method like nextIntegerBetween(int minInclusive, int maxExclusive), because of that many Java progarmmers, particularly beginners struggle to generate random numbers between a range e.g. random integers between 1 to 6 if you are creating a game of dice, or random number between 1 to 52 if you are creating a game of playing cards and you need to choose a random card, or most commonly random numbers between 1 to 10 and 1 to 100. Then, the question comes, how to solve this problem? How to generate random int values between a range? Well, you need to do a little bit of work.

5 Difference between an array and linked list in Java

The difference between an array and linked list is one of the frequently asked data structure and algorithm interview question and you might have seen it before on your telephonic or face-to-face interview. It is also a very popular question during practical exams in Computer Science degree courses e.g. B.E. and B.Tech. It's very simple and easy to answer but you just can't afford to miss this question in an interview. Both array and linked list are two of the most popular and fundamental data structure in Computer Science and Programming, and Java supports both of them. One of the traits of a good programmer is extensive knowledge of data structure and algorithm and that's why it's very important for you to learn the difference between array and linked list data structure and understand when to use an array over a linked list and vice-versa.

How to Convert a List into Map in Java 8 - Example Tutorial

One of the common tasks in Java programming is to convert a list to map and I have written about this in past and today we'll see how Java 8 makes this task easier. Btw, be it Java 7 or Java 8, you need to keep something in mind while converting a list to map because they are two different data structure. For example, the list allows duplicate elements but keys in a map must be unique, the value can be duplicated but a duplicate key may cause a problem in Java 8. Similarly, another concern is order. A list is an ordered collection but the map doesn't guarantee any order unless you decide to use LinkedHashMap, which keeps insertion order or TreeMap which keeps mapping in the sorted order of keys. This is one of the important details which many Java beginners forget and then spend hours to chase subtle bugs.

Top 10 Java 8 Tutorials and Courses - Best of Lot, Must Read

It's almost six months since Java 8 was released and there are so many Java 8 tutorials are written by Oracle, bloggers, and other peoples, but which should you read? Which tutorials are worth of your time? Actually, this question is asked to me by one of my reader called John, he was asking me about some good Java 8 tutorials, which he can read to start with. This encouraged me to take a look at some of the Java 8 tutorials available on the internet and form a list of best. I have just used three criterion, content, language and length. Because tutorials complement books, they should not be like the book. They should be small enough to complete in few hours and complete enough to give useful information. I also like tutorials, which discusses practical problems and examples.

How to Convert a LinkedList to an Array in Java? Example

You can convert a LinkedList to an array in Java by using the toArray() method of the java.util.LinkedList class. The toArray() method accepts an array of relevant type to store contents of LinkedList. It stores the elements in the array in the same order they are currently inside the LinkedList. By using the toArray() method you can convert any type of LinkedList e.g. Integer, String or Float to any type of Array, only catch is this you cannot convert a LinkedList to an array of primitives i.e. a LinkedList of Integer cannot be converted into an array of ints by using toArray() method, but you can convert it to array of Integer objects, that's perfectly Ok.

5 ways to Compare String Objects in Java - Example Tutorial

here are many ways to compare String in Java e.g. you can use equals() and equalsIgnoreCase() for equality check and compare() and compareTo() for ordering comparison. You can even use the equality operator == to perform reference based comparison e.g. to check both the String reference variable points to the same object. In general, equals() is used to check whether the value of given String is same i.e. they contain same characters in the same sequence or not e.g. "Groovy".equals("Groovy") will be true if you compare them using equals() method. You can also use equalsIgnoreCase() to check if they are equal irrespective of case e.g. "Apple" and "apple" will be same if you compare them using equalsIgnoreCase() method.

How to Count number of 1s (Set Bits) in Given Bit Sequence in Java

Good morning folks, In today's article, we are going to discuss one of the frequently asked bit manipulation based interview question, how do you count the number of set bits in given bit sequence?  Bit Manipulation is an important topic on programming interview and a good programmer should have sufficient knowledge and skill to work with binary numbers. This kind of questions tests that skill of the programmer. Sometimes, it is also asked as for how to count the number of 1s (ones) in given number? Both are the same question because 1 is also known as set bit.  For example, if given input is 1000110010 than your program should return 4, as three are only four set bits in this bit sequence.

Can you Make a Class Static in Java? Interview Question

This is one of the tricky questions in Java because there is no straight forward Yes and No answer here. You cannot make a top level class static in Java but Yes, you can make a nested class static in Java. In fact, it is even advised (see Effective Java) to prefer a nested static class in Java than normal inner classes. Now, the question comes what is a top level class and what is a nested class in Java? Well, you can declare multiple classes in a single Java source file. A class is said to be top level if it is not inside any other class and a class which is inside another class is known as nested class. You can create nested class inside another top level or another nested class in Java. This is the class which can be static in Java.

Top 20 Hibernate Interview Questions for Java J2EE Programmers

Hibernate is one of the most popular persistent frameworks in Java world. Hibernate offers object to relational (ORM) solution which frees Java developers from writing tedious, hard to read and cluttered JDBC code converting SQL columns into Object properties. Apart from freeing Java developer from writing JDBC and database interaction code, Hibernate also offers the out-of-box solution on caching, proxying and lazy loading which drastically improves the performance of your Java Web application. Given it's important in Java Web application development field Hibernate has become of one of the most sought-after skill and goes hand in hand with Spring framework. That's why Spring and Hibernate interview questions are also very popular in Java interviews, particularly for web development positions.

JDBC - Difference between PreparedStatement and Statement in Java

If you have worked with database interfacing with Java using JDBC API then you may know that the JDBC API provides three types of Statement for wrapping an SQL query and sending for execution to the database, they are aptly named as Statement, PreparedStatement, and CallableStatement. First one, Statement is used to execute normal SQL queries e.g. select count(*) from Courses. You can also use it to execute DDL, DML and DCL SQL statements. The second one, PreparedStatement is specialized to execute parameterized queries e.g. select * from Courses where courseId=?, you can execute this SQL multiple times by just changing the course parameters. They are compiled and cached at database end, hence quite fast for repeated execution.

Difference between ISNULL and COALESCE T-SQL Function in Microsoft SQL Server - Interview Questions

Even though both ISNULL() and COALESCE() function provides alternate values to NULL in T-SQL and Microsoft SQL Server e.g. replacing NULL values with empty String, there are some key differences between them, which is often the topic of SQL Server interview. In this article, you will not only learn the answer to this question but also learn how to use COALESCE and ISNULL function properly. One the main difference between them is that  COALESCE() is a standard SQL function but ISNULL() is a Microsoft SQL Server specific, which means it's not guaranteed to be supported by other database vendors like Oracle, MySQL or PostgreSQL.

How to Convert a Comma Separated String to an ArrayList in Java - Example Tutorial

Suppose you have a comma-separated list of String e.g. "Samsung, Apple, Sony, Google, Microsoft, Amazon" and you want to convert it into an ArrayList containing all String elements e.g. Samsung, Apple, Google etc. How do you do that? Well, Java doesn't provide any such constructor or factory method to create ArrayList from delimited String, but you can use String.split() method and Arrays.asList() method together to create an ArrayList from any delimited String, not just comma separated one. All you need to do is first split the given String on delimiter e.g. comma using the split() method, this will give you an array of String. Now, you can pass that array to Arrays.asList() method to create a List, but remember this would be fixed length list and not truly an ArrayList.

10 Examples of Array Data Structure in Java - Tutorial

Along with the String, the array is the most used data structure in Java. In fact, String is also backed by a character array in Java and other programming languages. It's very important for a Java programmer to have good knowledge of array and how to do common things with array e.g. initialization, searching, sorting, printing array in a meaningful way, comparing array, converting an array to String or ArrayList and doing some advanced slicing and dicing operation with an array in Java. Like my previous tutorials 10 example of HashMap in Java, I'll show you some practical example of array in Java. If you think, any important operation is not included, you can suggest their examples and I'll add them to this list.

Java Enum With Constructor Example

Java Enum with Constructor
Many Java developers don't know that Java Enum can have a constructor to pass data while creating Enum constants. This feature allows you to associate related data together. One example of passing arguments to enum Constructor is our TrafficLight Enum where we pass action to each Enum instance e.g. GREEN is associate with go, RED is associated with stop and ORANGE is associated with the slow down. This is really useful because it provides more context and meaning to your code. If you want, you can also provide one or more constructor to your Enum as it also supports constructor overloading like normal Java classes. This is very different from enum you have seen in C or C++, which is just a collection of fixed thing without any OOP power.

How to Implement a Power Function in Java - Coding Interview Problems

Even though the Java library has a power function, Math.pow() to calculate the power of a given number in Java, it's a common programming exercise for Java programmer to implement a power function. If you have used the Math class then you know that the java.lang.Math.pow(double a, double b) returns the value of the first number raised to the power of the second number and you need to do the same. In other words, you need to write a Java function to calculate the power of integer numbers for simplicity. The original method accepts a double value but you are allowed to use just integer but beware that power function may overflow.

Effective Java 3rd Edition by Joshua Bloch – A Must Read Book for Java Developers

Hello guys, you might have heard about it that Effective Java 3rd Edition is finally available. After 10 years of the long wait by Java programmers from all over the world, finally, an updated version of, probably the most popular Java book on the planet is released now. This new version covers the features and paradigm introduced in JDK 7, 8, and 9.  Joshua Bloch has done a great job in also updating most of the items to keep it relevant to the newer version. Apart from that, there is a whole new chapter added to explain best practices around Java 8 features. I know you don't need any reason to read this book, given its huge popularity and acceptance. Many startups which use Java,  particularly in India, are also distributing copies of this book as a New Year Gift.

Java 8 Default Methods FAQ - Frequently asked Questions and Answers

In last a couple of articles, I have to talk about default methods introduced in JDK 8. First, we have learned what is default method and why it is introduced in Java. Then we have seen the example of how you can use default methods to evolve your interface. After that we have analyzed does Java really support multiple inheritances now in JDK 8 (see here) and how will Java handle the diamond problem that will arise due to default methods. For example, what will happen if a class extend a class and implement an interface and both contain a concrete method with same method signature? Will a diamond problem arise? How will Java handle that and how you can solve it, and the difference between abstract class and interface in Java 8?  Once you went through those articles, you would have a good knowledge of default methods in Java 8.

Difference between wait() and join method in Java thread

Though both wait() and join() methods are used to pause the current thread and have a lot of similarities they have different purposes. One of the most obvious differences between the wait() and join() method is that former is declared in java.lang.Object class while join() is declared in java.lang.Thread class. This means that wait() is related to the monitor lock which is held by each instance of an object and join method is related to Thread itself. The wait() method is used in conjunction with notify() and notifyAll() method for inter-thread communication, but join() is used in Java multi-threading to wait until one thread finishes its execution.

Difference between @SpringBootApplication vs @EnableAutoConfiguration annotations in Spring Boot

Even though both @SpringBootApplication and @EnableAutoConfiguration can be used to enable the auto-configuration feature of Spring Boot there is a subtle difference between them. The @SpringBootApplication does much more than what @EnableAutoConfiguration do. It's actually a combination of three annotations: @Configuration which is used in Java-based configuration on Spring framework, @ComponentScan to enable component scanning of components you write e.g. @Controller classes, and @EnableAutoConfgiuration itself, which is used to enable auto-configuration in Spring Boot application. Spring Boot designers realize that these three annotations are frequently used together so they bundled them into @SpringBootApplicaiton. Now, instead of three annotations you just need to specify one annotation on your Main class.

How to use Callable Statement in Java to call Stored Procedure? JDBC Example

The CallableStatement of JDBC API is used to call a stored procedure from Java Program. Calling a stored procedure follows the same pattern as creating PreparedStatment and than executing it. You first need to create a database connection by supplying all the relevant details e.g. database URL, which comprise JDBC protocol and hostname, username, and password. Make sure your JDBC URL is acceptable by JDBC driver you are using to connect to the database. Every database vendor uses different JDBC URL and they have different driver JAR which must be in your classpath before you can run the stored procedure from Java Program.

A Beginners Guide to Package in Java

If you are learning Java then you might have come across package concept and if you are wondering what is package and why should we use it then you have come to the right place. In this article, I will explain what is package in Java and other stuff around the package, including some best practices which using the package in Java. In the simplest form, a package is a way to organize related functionality or code in single place in Java. If you look from File System perspective then a package in Java just represent a directory where Java source file is stored in compilation and class files are stored after compilation. For example, if you create a class HelloWorld in a package called com.java67.welcome; then it will reside under directory com/java67/welcome in the source tree and you can view that in your IDE like Eclipse or Netbeans or even by navigating to file system.

Java CountDownLatch Example - Multithreading and Concurrency Tutorial

The CountDownLatch is an important concurrency utility class which was added in JDK 1.5 but unfortunately, many Java developers still struggle to understand and use this powerful tool. You can use CountDownLatch if you are spawning multiple threads to do different jobs and want to know when exactly all tasks are finished so that you can move to next stage. In other words, you can block a thread until other threads complete their task. One of the good examples where you can use CountDownLatch is an application which downloads data from a database or another application. For example, we are creating a Java program to download all Udemy courses. Since Udemy has thousands of courses, you create different threads to download different categories e.g. technology, development etc.

5 Free Python Courses for Beginners to Learn Online

Hello guys, If you are a beginner looking for some Free Python resources to start your programming journey then you have come to the right place. Earlier, I have shared a couple of free Python Programming eBooks sand today I'll share a couple of good Python programming courses which are absolutely FREE!! You can take these online courses to learn Python at your own pace, at your own time, and at your place. This is a great advantage of online learning, the flexibility it provides is just awesome.  You just need a laptop or a smartphone with an internet connection and you can learn anything. Btw, before to start with the list of courses to learn Python programming I want to congratulate you for making the right decision to start your programming journey with Python.

Difference between Abstract class and Interface in Java 8

Ever since JDK 8 has allowed concrete (non-abstract) methods on the interface like default and static methods, many of my readers have asked me how should they answer the classical abstract class vs interface questions. Earlier, an interface cannot have any concrete methods and that was the main difference between abstract class and interface but now that is not the case. In this post, I'll revisit this hugely popular Java interview question in light of Java 8 changes. As I said, before JDK 8, the level of abstraction was the clear-cut difference between abstract class and interface i.e. interface was the purest form of abstraction which only defines what interface is supposed to do without specifying how they should be implemented, in other words, it only declares API methods and leaves implementation to its subclasses.

How to work with Files and Directories in Java

The File API is one of the important parts of any programming language or API and even though Java's file API both new and old, are powerful, they are not intuitive enough compared to other languages e.g. Python. Apart from knowing the essential classes and abstractions e.g. File, InputStream, OutputStream, Reader, Writer, Channel etc, you also need to know and remember some nitty gritty detail to avoid subtle issues. There are many articles out there on the internet which can teach you how to read and write data from the file but there are very few which will tell you to do it in right way.

How to implement Radix Sort in Java - Algorithm Example

The radix sort, like counting sort and bucket sort, is an integer based algorithm (i.e. the values of the input array are assumed to be integers). Hence radix sort is among the fastest sorting algorithms around, in theory. It is also one of the few O(n) sorting algorithm along with a bucket and counting sort. The particular distinction for radix sort is that it creates a bucket for each cipher (i.e. digit); as such, similar to bucket sort, each bucket in radix sort must be a growable list that may admit different keys.

How to convert primitive int value to a Long object in Java?

Suppose you have an int variable but the part of the application is expecting a Long object, how do you convert a primitive int to a Long object in Java? It shouldn't be a problem, right? after all long is a bigger data type than int, so all int values are acceptable as long, but we also need a Long object, not just the long primitive value. Now, the problem is reduced to converting a long primitive to Long object, which is not really a problem if you are running on JRE version higher than Java 5. But, sometimes autoboxing is not efficient e.g. when you have to convert multiple long values into the Long object in a loop. A better way to convert your long primitive to the Long object is by using static factory methods like Long.valueOf(long l), which was originally meant to convert long primitive values to a Long object, prior to Java 5, but, also works fine with int primitive.

Difference between OCAJP7 and OCAJP8 Certification - 1Z0-803 vs 1Z0-809

One of the frequently asked questions asked by most of the OCAJP certification candidates is, what are the differences between OCAJP 8 and OCAJP 7? And,  Which one Java developers should go for in 2018? OCAJP7 or OCAJP8? The obvious answer to this question is the latest Java version of the exam i.e. OCAJP 8. Since it's already more than 5 months since Java 9 is out but there is no OCAJP 9 certification, the OCAJP 8 should be the exam, Java developer should pursue in 2018. The question is more for those who are looking to become certified Java developer in quick time and doesn't know Java 8 yet e.g. experienced Java developers who have extensively worked in Java SE 6 and prior version but don't have any Java certification yet.

Java 8 Stream findFirst() and filter() Example

Suppose, you have a list of prime numbers and you need to find the first prime number which is greater than a given number? How do you find it? Don't tell that you will loop through the list and check each element and return the first element which is greater than the given number. Well, that's right but that's not what you should do in Java 8. That's good for Java 7 or earlier version but Java 8 offers you many better alternatives and one of them is Stream. You can use the Stream class along with filter() and findFirst() methods to find out an element based upon a Predicate, a functional interface for defining a condition which returns a boolean.

Top 15 Spring Boot Interview Questions with Answers for Java/JEE Programmers

Hello guys, if you are preparing for your next Java interview and Job description mentioned about Spring framework, then you should also prepare some Spring Boot interview questions to avoid disappointment. The Spring Boot is now the standard way to use Spring framework for Java development and almost all the companies are moving from the traditional way of using Spring Framework to more modern Spring Boot way. Gone are the days, where questions like have you used Spring Boot was asked to the developer. Nowadays interview expects more knowledge of Spring Boot from candidates and there are reasons for it, which we'll explore in this article.

Top 20 Essential Java Interview Questions with Answers for Freshers with 1 to 2 years Experienced

If you are grad looking for an internship position in a company which uses Java, or a fresher, just out from college and looking out for Java development position, then this post is for you. I have attended, taken and participated in a different level of Java interviews, and I can say there is a huge difference between them, which is not surprising because you obviously want to ask different level questions based upon whether the candidate is fresher or experienced. Similarly, the question at phone interview, written test, and face to face interviews, keeping this in mind, and give you always have a limited amount of time before going for an interview, It's important to prepare right set of questions.

Binary tree InOrder traversal in Java using Recursion

The InOrder traversal is one of the three popular ways to traverse a binary tree data structure, other two being the preOrder and postOrder. During the in order traversal algorithm, left subtree is explored first, followed by root, and finally nodes on right subtree. You start traversal from root then goes to left node, then again goes to left node until you reach a leaf node. At that point in time, you print the value of the node or mark it visited and moves to right subtree. Continuing the same algorithm until all nodes of the binary tree are visited. The InOrder traversal is also known as left-node-right or left-root-right traversal or LNR traversal algorithm.

Top 35 Java String Interview Questions with Answers

The  String class and concept is a very important class in Java. There is not a single Java program out there which is not using String objects and that's why it's very important from interview point of view as well. In this article, I am going to share 35 String based questions from different Java interviews. It includes questions on java.lang.String class as well as string as data structure e.g. some coding questions something like I have shared in my earlier article about 75 Coding questions to Crack any Programming Job interviews.  You can use this list to refresh your knowledge about String in Java as well as to prepare for your next Java interview. If you have any good String questions which are not on this list, feel free to drop a note and I'll include in this list.

How to remove duplicates from Stream in Java 8 - Stream.distinct() Example

You can use the Stream.distinct() method to remove duplicates from a Stream in Java 8 and beyond. The distinct() method behaves like distinct clause of SQL which removes duplicate rows from the result set. The distinct() is also an intermediate method which means it will return a new Stream without duplicates, which can be used for further processing. Like other methods of Stream class e.g. map() or filter(), distinct() is also lazy and it will not remove duplicate elements until you call a terminal method on Stream.  The actual processing of Stream pipeline starts only after calling terminal methods like collect() or forEach().

Top 5 Books to Learn Grails Framework for Java and Groovy Developers.

Earlier, I have shared some of the must-read Groovy books and today, I'll share some of the best books to learn Grails for Java developers. Grails is a web application development framework completely written in Groovy. The Grails and Gradle framework are built using Groovy language. Grails is the framework to develop a web application using Groovy. The concepts within Grails, like interceptors, tag libs, and Groovy Server Pages (GSP) are very similar to what we have in Java. You'll be amazed at how quickly you can have a first-class web application up and running from ground zero. Grails includes everything you need in a single zip file on a web server (Jetty), a database (HSQLDB), Spring, Hibernate, even a Groovy version of Ant called GANT.

3 Ways to Convert String to Short in Java - Example Tutorial

In last a couple of examples, I have taught you how to convert String to Integer, Long, Double, Float, Boolean, and Byte in Java and today I will show you how to convert String to Short in Java, but before that let's revise what is short data type in Java. The short is an integral data type similar to the int but it only takes 2 bytes to store data as compared to 4 bytes required by an int variable. Since it takes only 2 bytes or 16 bits to store data, the range of short is also shorter than int. It ranges from -32,768 to 32767 (inclusive) or -2^15 to 2^15 -1. You might be wondering why upper bound is 255 and lower bound is -256 but that's because we have included zero in between.

Java - String charAt Example - How to get first and last characters

The charAt(int index) method of java.lang.String class can be used to retrieve a character from given index. The method returns a character, you can see its return type is char. The index starts from zero and ranges to length() - 1 where length() return the length of String. It's similar to an array where the first element is stored at zeroth index and the last element is stored at length -1 index because String is nothing but backed by a character array. If the value of the index is invalid i.e. it's lower than zero or negative or higher than length - 1 then this method throws an IndexOutOfBoundsException. In this article, I'll show you a couple of example of how to use the charAt() method to retrieve a character from String in Java.

Java 8 Optional Example - isPresent(), OrElse() and get()

The Optional class in Java is one of many goodies we have got from the Java 8 release. If you use correctly, Optional can result in clean code and can also help you to avoid NullPointerException which has bothered Java developer from its inception. Even though many of us have used null to indicate the absence of something, the big problem is that if you call a method or access a field on the null object (except static fields), you will get a NullPointerException and your whole program may crash. The bigger problem is to find the faulty code or root cause because NullPointerException only indicates the line when you try to access field or variable from a null object but how does that null is get created on the code is unknown.

2 Ways to Add Binary Numbers in Java - Coding

In the last article, I have shown you how to subtract binary numbers in Java and today, you will learn the opposite i.e. how to add binary numbers in Java. You can do binary addition in Java either by writing your own logic or by taking advantage of the Java API, which allows you to convert a binary String into a binary number. Though, if you want you can also use the logic I have shared in my earlier post about how to check binary numbers to verify input before converting it to a binary number. In this article, we'll take a look at both methods of adding two binary numbers in Java.

JDBC - How to get Row and Column Count From ResultSet in Java

One of the common problem in JDBC is that there is no way to get the total number of records returned by an SQL query. When you execute a Statement, PreparedStatement, or CallableStatement using execute()or executeQuery() they return ResultSet and it doesn't have any method to return the total number of records it is holding. The only way to find the total number of records is keeping the count while you are iterating over ResultSet while fetching the result. This way, you can print the total number of rows returned the SQL query but only after you have processed all records and not before, which may not be the right way and incur significant performance cost if the query returns a large number of rows.

How to change date format of String in Java 8

One of the common programming task in Java is to change the date format of a given Date or String. For example, you have something like "2017-01-18 20:10:00" and you want to convert it that date into "2017-01-18", or you want to convert from dd-MM-YY to MM-dd-YY or to any other format of your choice and need, but a valid date format as per Java specification. How will you do that? Well, it's not that difficult. It's just a two-step process. In the first step, you need to parse String to create an equivalent date using current format and then once you got the date, you need to again convert it back to String using the new format. The same process is repeated in both Java 8 and before, only corresponding API and classes changes.

Mergesort in Java - Algorithm Example and Tutorial

The Merge sort algorithm is a divide and conquers algorithm. In the divide and conquer paradigm, a problem is broken into small problems where each small problem still retains all the properties of the larger problem -- except its size. To solve the original problem, each piece is solved individually; then the pieces are merged back together. For example, imagine you have to sort an array of 200 elements using the selection sort algorithm. Since selection sort takes O(n^2) time, it would take about 40,000-time units to sort the array. Now imagine splitting the array into ten equal pieces and sorting each piece individually still using selection sort. Now it would take 400-time units to sort each piece; for a grand total of 10*400 = 4000.

Java - Convert String to Boolean Example

There are two ways to convert a String to boolean in Java, first, by using Boolean.parseBoolean() method and second, by using Boolean.valueOf() method.The parseBoolean() method returns an equivalent boolean value of given String, for example, if you pass "true" it will return the primitive boolean value true. Similarly, if you pass "false" it will return false. The good thing about this method is that it is case insensitive, which means if you pass "true", "TRUE", or "True" you will still get a true boolean value.

How to Subtract two Binary Numbers in Java - Solution

Binary subtraction is very similar to binary addition which we have learned in the last article. In this tutorial, you will learn how to subtract two binary numbers. Similar to the last article, we'll see two ways, first by converting binary String to a binary number and then doing subtraction. You can use the Java API Integer.toString(number, radix) for that. On second solution you will learn to develop the logic to perform binary subtraction in Java program by using rules you might have learned in your computer classes. Here is a little summary of how binary subtraction works.

Java String 101 - Everything You Want to Know about String in Java

someone might question that why do we need another article about string in Java, haven't we had enough about the string is already written? Yes, I agree there are a lot of articles related to Java string covering topics like how to use Java String, an example of Java string and almost everything you can do with string in Java. But, I wanted to document my experience of using String in Java and some nasty and little-known things I discovered about the Java String class, which may not be obvious to many Java developers. A string is available in almost every programming language and its probably the most used data structure or a data type, hence a good knowledge of String is very important for every Java developers.

Difference between OCAJP and OCPJP Certification Exams for Java Programmers

Earlier when Sun Microsystems was in charge of Java, the popular Java certifications were called "Sun Certified Java Programmer" or "SCJP" and that time there was just one exam, you need to pass to become a certified Java Developer, but when Oracle took over Sun Microsystems on 2010, the SCJP goes away and OCAJP and OCPJP born. Since Oracle already has his certifications for database administrations e.g. OCA which stands for Oracle certified associates and OCP, which stands for Oracle Certified Professional, it introduces new Java certifications to match their existing hierarchy and they are known as OCAJP and OCPJP in the Java world.

3 ways to convert String to byte array in Java - Example Tutorial

Today, I am going to discuss one of the common tasks for programmers, converting a String to a byte array. You need to do that for multiple reasons e.g. for saving content to a file, sending over a network or maybe some other reason. Suppose you have a String "abcd" and you want to convert it into a byte array, how will you do that in a Java program? Remember, String is made of the char array, so it involves character to byte conversion, which is subject to character encoding intricacies. Thankfully, Java provides a convenient getBytes() method to convert String to byte array in Java, but unfortunately, many developers don't use it correctly. Almost 70% of the code I have reviewed uses getBytes() without character encoding, leaving it on the chance that platform's default character encoding will be same as of the source String.

Eclipse - Unsupported major.minor version 53.0, 52.00, 51.0 Error in Java

The UnsupportedClassVersionError is a big nightmare for Java developers, probably the next biggest after NoClassDefFoundError and ClassNotFoundException but its slightly easier to solve. The root cause of this error is that your code is compiled using higher JDK version and you are trying to run it on the lower version. For example, the Unsupported major.minor version 53.0 means your code is compiled in JDK 9 (the class version 52 corresponds to JDK 9) and you are trying to run it on any JRE lower than Java 9, probably JDK 8, 7, or 6.

What is difference between an int and Integer in Java?

The first and foremost difference between an int and Integer or a char and Character is that former is a primitive data type while later is a class, also known as wrapper class because they wrap primitive data type inside it. When you first start learning Java, you start with primitive data types e.g. int, long, char, byte, boolean, float, and double but slowly you learn about Object and sometime later you know about Integer, Long, Character, Byte, Boolean, Float, and Double. At this point in time, you may wonder, what is the real difference between an int and Integer? isn't both same? We can pass Integer where int is expected and vice-versa then why on the earth we have both int and Integer?