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How to send HTTP Request from a 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 the java.net package to send a simple HTTP request in Java. But, first, let me answer your first question, is it possible to send an HTTP request in Java? Yes, it's possible and you can send any kind of HTTP request like 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.
Difference between static initializer block vs instance initializers in Java? Example
In Java, you can initialize member variables or fields in the same line you declare, in the constructor, or inside an initializer block. There are two types of initializer blocks in Java, static initializer block to initialize static variables and instance initializer block to initialize non-static fields. As the name suggests, the main difference is their purpose, instance initializer block if for instance variables, and static initializer block is for static variables. Another key difference between them is the time of execution.
How to validate phone numbers in Java? Google libphonenumber library Example Tutorial
Hello guys, if you are wondering how to validate if a given number or string is a valid phone number in a Java application then you are not alone. It's a common requirement to validate phone numbers for a Java web application, much like validating email addresses. Unfortunately, Java doesn't provide any built-in method to carry out this kind of common validation, I would love to have a validation package in Java, but don't worry there must be an open-source library to cover this deficiency, right? Yes, there is Google's phone number library which allows you to validate any phone number both international, USA specific, or any country-specific.
How to convert String to int or Integer data type in Java? Example Tutorial
Hello guys, if you are wondering how to convert a String variable to int or Integer variable in Java then you have come to the right place. Earlier, I have showed how to convert Integer to String in Java and today, you will learn about how to convert String to int or Integer variable in Java. There are 3 main ways to convert String to int in Java, first, by using the constructor of Integer class, second, by using parseInt() method of java.lang.Integer, and third, by using Integer.valueOf() method. Though all those methods return an instance of java.lang.Integer, which is a wrapper class for primitive int value, it's easy to convert Integer to int in Java.
3 ways to Convert Integer to String in Java [Example]
Hello guys, this is the second part of the 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 that directly converts an Integer object to a String like the 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 a String in Java.
Difference between private and final class, method, and variables in Java?
Hello guys, one of the common questions among Java beginners is what is the difference between a private and final keyword in Java? The confusion arises because they are very similar and used in a similar context. For example, you can make a class, a method, and variable final as well as private. Both put some kind of restriction like you cannot override a final method in Java and the private method is not even accessible outside the class, so obviously you cannot override it.
What is InstanceOf keyword in Java [Example Tutorial]
The Java programming language and JVM are full of hidden gems and even though I am using Java for more than a decade I still get surprised by features that I didn't know for quite some time like shutdown hook, covariant method overriding, and JVM option to refresh DNS cache. The instanceof operator is also one of the rarely known features of Java, It is used to check if an object is the instance of a particular class or not. It returns true if the object is an instance of the class, otherwise, returns false. You might have seen usages of the instanceof keyword in Java while overriding the equals() method. Since for checking equality of two instances, the first step is to verify whether they are the instance of the same object or not, you can use the instanceof operator there.
Difference between trustStore vs keyStore in Java SSL
If you are confused between truststore and keystore and looking to find what exactly they mean then you have come to the right place. Earlier, I have shared free Java courses and today, I am going to tell you the difference between trustStore and keyStore in Java. Both trustStore and keyStore are important but confusing concepts and constantly tormented Java developers when they connect to servers using SSL. The main difference between trustStore vs keyStore is that trustStore (as the name suggest) is used to store certificates from trusted Certificate authorities(CA) which are used to verify certificate presented by Server in SSL Connection while keyStore is used to store the private key and own identity certificate which program should present to other parties (Server or client) to verify its identity.
SQL Join Tutorial - How to use JOIN Multiple Tables in SQL query? MySQL Example
Hello guys, if you are wondering how to join multiple tables in SQL to produce a combine result which contains columns from all tables but not sure how to do it then you have come to the right place. SQL Join is one of the basic concepts while working in databases or tables but yet less understood and most confusing topic for beginners and even intermediate developers. I compare Joins in SQL with Recursion in programming in terms of confusion because I have found that these two topics are special in their nature and you can't get it right with casual reading until you understand the concept and its various well. Things get worse when the table locked due to such SQL Join queries which were fired without knowing how much time it would and how big the result set could be.
Difference between Primary and Foreign keys in SQL [Answer]
The database is a collection of tables and a table is the collection of rows or records. A primary key is the data to uniquely identify a row in the table. For example, if an Employee table has millions of rows and emp_id is a primary key then it can uniquely identify that row. You can use this primary key to retrieve (SELECT) the row, update the row, and delete the row. In SQL, a table can have only one primary key but it can contain more than one column. There are two types of primary key, a simple primary key, and a composite primary key.
When to use TRUNCATE vs DELETE command in SQL?
While working with the database we often need to delete data, sometimes to create more space, sometimes just remove all data to make the table ready for the next day's transaction, or sometimes just selectively remove stale data. SQL provides a couple of handy commands to remove data e.g. truncate, delete and drop. The last one is a bit different because instead of removing data it just deletes the table. What is the difference between truncate and delete command in SQL or when to use truncate vs delete is one of the most frequently asked SQL interview questions?
How to create an ArrayList from array in Java? Example
One of the common problems faced by junior and less experienced Java develoeprs is converting an arrray to ArrayList e.g. they are getting an array from somewhere in their code and then want to create an ArrayList out of that, so that they can add more elements and use other library methods which operates with ArrayList or List. The simplest way to convert an array to ArrayList is by usign the Arrays.asList() method, which acts a bridge between Collection classes and array data structure. This method returns a List which contains elements from array.
Difference between Proxy and Decorator Pattern in Java
Though both Proxy and Decorator pattern looks very similar to each other
structurally, there are some key differences between them. Main difference
between Decorator and Proxy patterns comes from their Intent. Proxy word has a
long standing meaning and in software world also a Proxy class stands for its
implementation class, which presents lots of options to programmer, resulting in
different kinds of proxy objects like remote proxy, virtual proxy, and
protection proxy. On the other hand, Decorator pattern is used to add new
functionality into existing object without modifying it's class. So their usage
is entirely different.
Unix command to find IP address from hostname - Linux example
The IP address from hostname in UNIX
In this Unix command tutorial, we will see how to find the IP address of
any host in a UNIX based system, like Linux, Solaris, or IBM AIX. In general
hostname and IP address are two important things about any host in a UNIX based
network. You always need either a hostname
or IP address to connect to any host. Sometimes you want to find the IP address of the localhost, sometimes the IP address of another host on the network, etc. We have shown
some techniques to find the IP address from hostname in UNIX and here we will see is a particular list of
UNIX commands to get the IP address of local host or host on which you are working along
with any other host for which we know hostname.
How to find Files with Matching String in Linux? grep -l command Example
The grep command from Linux is one of the powerful commands to find files containing some text, but when you use grep, it not only print the file name but also the line, which is including the matching text. This is actually required and needed in most situations. Still, sometimes you only want to grep to show just filename and path and not the matching text. For example, when you are searching for some configurations like a Linux or database hostname across all configuration files in your application host, then you just want to see which file has contained those references.
13 Java Serialization Interview Questions with Answers for 3 to 5 Years Experienced
There is no doubt that Java is vast and there are some Java topics which many Java developers rarely explore in work but they are important from a Java interview point of view. Serialization is one of them which is rarely used in practice but quite popular during Java interviews. It's also one of the difficult topics to master and that's why I am going to share some frequently asked Java Serialization interview questions in this article. I don't know why people ask so many questions from Serialization if not everyone uses it but I have always seen some questions from Java realization. These are also the toughest and confusing questions to answer and more likely cannot be answered by an average Java developer.
10 Regular Expressions Every Java Programmer Should Learn
Regular Expression or regex or regexp is used for String or text matching. You specify a regular expression and then run input String to see if any String matches with your regular expression. There are a lot of use cases of regular expression e.g. you can do find and replace and you can actually search in a big log file for the expression or text you are looking it. Regular expression is not just limited to any programming language like Java but it present everywhere. You use Regular expression in Linux for pattern matching like with grep, find, sed and awk command. Even VI editor allows you to search words using regular expression and popular Windows text editor like Notepad++ and Edit Plus they also support regular expression for search and replace.
Difference between Set, List and Map in Java - Interview question
Set, List and Map are three important interfaces of the Java collection framework, and the difference between Set, List, and Map in Java is one of the most frequently asked Java Collection interview questions. Sometimes this question is asked as When to use List, Set and Map in Java. Clearly, the interviewer is looking to know that whether you are familiar with the fundamentals of the Java collection framework or not. In order to decide when to use List, Set or Map, you need to know what are these interfaces and what functionality they provide. List in Java provides ordered and indexed collection which may contain duplicates.
Difference between Heap and Stack Memory in Java? [Explained]
One of the many traits of a good programmer is how well he understands the fundamentals and if you want to check the fundamentals of a Java programmer then asking the difference between heap and stack memory is a good choice. Even though both are part of JVM and both consumer's memory allocated to the Java process, there are many differences between them like Heap memory is shared by all threads of Java application but Stack memory is local to each thread. Objects are created in heap memory but method frames are stored in Stack memory, and the size of heap space is much bigger than the small size of Stack in Java.
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