Java Platforms

There are four Java platforms or editions. These are:

1- Java SE (Java Standard Edition): 

This includes Java programming APIs like java.lang, java.io, java.net, java.util, java.sql, java.math, etc. It includes core subjects such as OOPs, String, Regex, Error, Multithreading, I / O Flow, Networking, AWT, Swing, Reflection, Set, etc.

2- Java EE (Java Enterprise Edition): 

It is used to develop web and enterprise applications. It is built on the top of the Java SE platform. It contains topics such as Servlet, JSP, Web services, EJB, JPA, etc.

3- Java ME (Java Micro Edition): 

A micro platform which is mainly used to develop mobile applications.

4- Java FX: 

To develop rich internet applications, Java FX is used. It uses a lightweight user API.

Prerequisite:

To learn Java, You must have the knowledge of basic c/c++ programming language.

Example:

The following Java example is used to check if a number is positive or negative using if-else.

public class PositiveNegative { 

 

public static void main(String[] args) { 

 

double number = 12.3; 

 

// true if number is less than 0 

if (number < 0.0) 

System.out.println(number + " is a negative number."); 

 

// true if number is greater than 0 

else if ( number > 0.0) 

System.out.println(number + " is a positive number."); 

 

// if both test expression is evaluated to false 

else 

System.out.println(number + " is 0."); 

} 

}

When you run this program, the output will be:

   12.3 is a positive number.

If you change the value of number to a negative number (say -12.3), the output will be:

    -12.3 is a negative number.

In the above example, it is clear how variable ‘number’ is hacked to be positive or negative, by comparing it to 0.