How to Convert String to LocalDate, LocalTime, LocalDateTime and ZonedDateTime in Java? Example Tutorial

The JDK 8 added a new Date and Time API (JSR 310) which introduces new date and time classes like LocalDate, LocalTime, LocalDateTime, and ZonedDateTime. Now, if you have a String e.g. "2016-12-14 03:30" then how do parse it to LocalDate, LocalTime, LocalDateTime and ZonedDateTime? Similarly, if you have an instance of those classes how you can format to the String you want e.g. in dd/MM/yyyy format, or USA or UK format? Well, Java 8 provides a utility class called DateTimeFormatter which can be used to parse/format dates in Java 8. It also provides several built-in formatter e.g. ISO date format and other to facilitate formatting of dates to String.

How to convert JSON to Map in Java 8 without using third party libraries like Jackson or Gson

Hello guys, If you are working with JSON data then you may know that JSON is collection of key value pairs and that's why many times, you also need to convert them into a Map in Java. While there are many Java libraries like Jackson and Gson which provides support of parsing JSON to Java objects, there is not much support for JSON parsing or manipulation on standard JDK. While JSON parsing is still a long overdue, starting with JDK 8u60+ the built-in Nashorn engine is capable to convert JSON content into java.util.Map. No external dependencies are required for parsing JSON in to Map as you will learn in this article.

Can You Override static method in Java? Method Hiding Example

Can we override the static method in Java?

This is one of the most popular Java interview questions. The answer to this question is No, you cannot override the static method in Java because the method overriding is based upon dynamic binding at runtime and static methods are bonded using static binding at compile time. This means static methods are resolved even before objects are created, that's why it's not possible to override static methods in Java. Though you can declare a method with the same name and method signature in the subclass which does look like you can override static methods in Java but in reality that is method hiding.

Top 30 Stack and Queue Data Structure Interview Questions for Practice

Hello guys, stack and queue are two fundamental data structures which are used on many applications and algorithms. For example, you can use stack to convert a recursive algorithm to iterative one, which is more safe in production and no risk of StackOverFlowError. Similarly, queue is used in many asynchronous algorithms like producer consumer pattern or publish subscribe pattern to exchange messages. Because of that, they are also quite popular on coding interviews, particularly on Java developer interviews. In the past, I have shared 100+ data structure questions as well as String coding problems, array questions, linkedlist questions, recursion questions and even dynamic programming questions but I have not shared stack and queue related questions before.

3 ways to check if checkbox is selected in jQuery - Example Tutorial

So, you have a checkbox and you want to check if its selected or not at runtime using jQuery. If that's what you want then continue reading. A checkbox is an HTML element with type="checkbox" and checked property is used to find out whether a checkbox is selected or not. There are several ways to find if your checkbox has this property or not in jQuery e.g. by using :checked, a pseudo selector or by using is() jQuery function or by using prop() function which is available from jQuery 1.6 onward. In this article, we will see examples of these approaches to check if a check box is checked or not.

Top 10 Frequently asked SQL Query Interview Questions Answers

In this article, I am giving some examples of SQL queries which is frequently asked when you go for a programming interview, having one or two year experience in this field. Whether you go for a Java developer position, QA, BA, support professional, project manager, or any other technical position, may interviewer expects you to answer basic questions from Database and SQL. It's also obvious that if you are working for one or two years on any project there is a good chance that you come across to handle databases, writing SQL queries to insert, update, delete and select records.

Top 100 Data Structure and Algorithm Interview Questions for Java Programmers

Data structure and algorithms are a 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, it's expected from a program to have strong knowledge of both basic data structures, like the array, linked list, binary tree, hash table, Stack, Queue, and advanced data structures like the binary heap, trie, self-balanced tree, circular buffer, etc.

How to remove duplicates from Collections or Stream in Java? Stream distinct() Example

Hello guys, if you wonder how to remove duplicates from Stream in Java, don't worry. You can use the Stream.distinct() method to remove duplicates from a Stream in Java 8 and beyond. The distinct() method behaves like the distinct clause of SQL, which eliminates duplicate rows from the result set. The distinct() is also a standard method, which means it will return a new Stream without duplicates, which can be used for further processing. Like other methods of Stream class, I mean, map(), flatmap(), or filter(), distinct() is also lazy, and it will not remove duplicate elements until you call a terminal method on Streams like collect or forEach().

5 Examples of map() and flatMap() in Java 8 Stream

The map() and flatMap() are prince and princess of functional programming in Java. They are two powerful methods of Stream API which I believe every Java developer should be aware of and should also master it. You can use map() and flatMap() for data transformation, dealing with database operations where you need to convert one object to another while saving or reading from database. You can also use them for parsing and formatting as well as when you want to remove boiler plate code and make your data pipeline concise. The map() function is used in functional programming to transform each element of Stream into another element.

Top 21 String Programming and Coding Interview Questions With Solutions

In this article, I am going to share 21 of the most common String-based Programming and Coding interview questions from Java developer interviews. These questions require you to write code to solve the problem and they are different from traditional Java String questions like how the substring method works in Java? or when to use the intern() method of String in Java? Since coding and problem solving are an important part of any programming job interview, it's imperative that you know how to solve them in time and in a pressure situation, which comes only after doing practice with the right set of questions. Since these questions are already tried and tested and appeared in many interviews, they will provide you the experience you need to crack your coding interview.

How String concatenation works in Java?

You can concatenate multiple String using + operator in Java. Even though Java doesn't support operator overloading, + operator is special, it performs addition if given operands are numeric and does String concatenation if one of them is String. Why it's important to know how String concatenation works? Well, more often that you can live without this knowledge but if you want to master Java then why not know little more detail. Apart from that it also helps you to avoid a performance mistake, which many Java devleoper do, concatenating String inside loop. When you concate two String literal e.g. "abc" + "cde" then compiler do this concatenation at compile time and this doesn't involve StringBuilder.

Concatenating two String literal

Concatenating String literal and String variable.

Things to remember:

1) Don't concatenate String in loop because Java creates a new StringBuilder() every iteration.

2) If two String literal are concatenated i.e. "Java" + "Script" then it happens at compilation time

2) When you concatenate a String literal and a String object, or two String object then it happens at runtime.

That's all about how String concatenation works in Java.

How to enable or disable form elements using jQuery? Examples

In last couple of tutorials you have learned how to get all selected checkbox and radio buttons, and in this tutorial, you will learn how to enable/disable form elements using jQuery. A form element e.g. a textfield, radio buttons and checkbox, all represented using input tag can be enabled or disabled by adding an attribute called "disabled". It's similar to "checked" attribute we have seen for checkbox and radio buttons. If this attribute is not present then element is enable, but if this attribute is present then you can use disabled=true to disable the form element and disabled=false to enable the form elements as shown in our example. Like previous example of checking/unchecking checkbox, you can use prop() jQuery function to enable/disable form element if you are running on jQuery 1.6 or higher version and attr() function if you are running on jQuery 1.5 or lower version.

How to shuffle a List in Java? Collections.shuffle() Example

Hello guys, if you have a List of numbers and you want to shuff it but don't know how then you have come to the right place. Shuffling is an important technique which is used quite a lot on coding games like number guessing games and card games., The java.util.Collections class provides shuffle() method which can be used to randomize objects stored in a List in Java. Since List is an ordered collection and maintains the order on which objects are inserted into it, you may need to randomize elements if you need them in a different order. Collections.shuffle() method uses default randomness to randomize elements but you also have an overloaded version of shuffle() to provide an instance of the java.util.Random object, which can be used to randomize elements.

How to Compare Two Dates in Java? Check If They Are Equal, Later or Earlier - Examples

There are multiple ways to compare two dates in Java, it also depends on what exactly comparison means. If you are looking to compare two dates to find out whether they are equal or not, then you can simply use the equals() method of java.util.Date class. This method will return true if both dates are equal, precisely both have the same millisecond value. If you are looking to find out whether a date comes before or after another date then you have 3 choices, you can use the compareTo() method of java.util.Date class, or you can use before() and after() method of Date class, or you can use before() and after() method of Calendar class. I suggest leveraging the before() and after() method of the Date class, they are more readable and easy to use.

What is transient variable in Java? Serialization Example

What is a transient variable in Java?

transient variable in Java is a variable whose value is not serialized during Serialization and which is initialized by its default value during deserialization, for example for object transient variable it would be null. This behavior can be customized by using a custom Serialized form or by using the Externalizable interface. A transient variable is used to prevent any object from being serialized and you can make any variable transient by using the transient keyword. You cannot make a local variable transient through and it's only the member variables which can be transient.

Difference between HashSet and HashMap in Java? Answered

HashSet and HashMap in Java
Hello friends, if you have given Java developer interview then there is good chance that you may have come across questions like Difference between HashSet vs HashMap or HashSet vs TreeSet etc. In this article, we are going to discuss differnece between HashMap and HashSet, two of the popular Collection classes from JDK. The HashSet vs HashMap is a classical Java Collection interview question that focuses on What are differences between HashSet and HashMap in terms of features, usage, and performance. If you are in Java programming even for a year or so, you are likely to be familiar with What is HashSet in Java and What is HashMap in Java, these two are the most popular collection classes.

What is PATH and CLASSPATH in Java? Path vs ClassPath Example

What is PATH and CLASSPATH in Java
The PATH and CLASSPATH are the two most important environment variables of the Java environment which are used to find the JDK binaries used to compile and run Java in windows and Linux and class files which are compiled Java bytecodes. From my personal experience I can say that PATH and CLASSPATH are the two most problematic things for beginners in Java programming language due to two reasons; first because in most Java courses nobody tells details of what is a PATH and CLASSPATH, What do PATH and CLASSPATH do, What is meaning of setting PATH and CLASSPATH, What happens if we do not set them, Difference between PATH vs CLASSPATH in Java or simply How Classpath works in Java, etc.

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