Why Java called platform independent?

Java is often called “platform-independent” because of its ability to write once and run anywhere (WORA). This platform independence is achieved through the following mechanisms:

1. Bytecode Compilation: Java source code is compiled into bytecode, which is a platform-independent intermediate code. This bytecode is not specific to any particular operating system or hardware architecture.
2. Java Virtual Machine (JVM): Java bytecode is executed by the Java Virtual Machine (JVM), which is specific to each platform. Each platform (such as Windows, macOS, or Linux) has its own JVM implementation, tailored for that specific system. When you run a Java program, the JVM interprets or compiles the bytecode into native machine code that can be executed by the host system’s hardware.
3. Write Once, Run Anywhere (WORA): Because Java bytecode is platform-independent, a compiled Java program can be executed on any system with a compatible JVM. As long as a JVM is available for a particular platform, you can run Java applications on that platform without modification. This concept of WORA is fundamental to Java’s platform independence.
4. No Platform-Specific Features: Java enforces a strict set of rules and standards, avoiding platform-specific features. This means that Java programs do not rely on features unique to a particular operating system, ensuring that they can run consistently across different platforms.

In summary, Java achieves platform independence by compiling source code into bytecode, which is then executed by platform-specific Java Virtual Machines. This approach allows Java applications to be written once and executed on any platform with a compatible JVM, making Java a truly platform-independent programming language.

Write once run anywhere in java

“Write Once, Run Anywhere” (WORA) is a fundamental principle of Java programming. It means that once a Java program is written and compiled into bytecode, it can be executed on any platform with a compatible Java Virtual Machine (JVM). Here’s a simple example to illustrate the concept of WORA in Java:

Let’s consider a basic Java program that prints “Hello, World!” to the console:

/*
      Zameer Ali
*/

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Once you’ve written this Java program, you can compile it using the Java compiler (javac), which will generate a bytecode file (HelloWorld.class).

javac HelloWorld.java

Now, the compiled bytecode (HelloWorld.class) can be run on any platform with a JVM. You don’t need to modify the source code or recompile it for different operating systems. For instance, to run the program, you use the java command:

java HelloWorld

Whether you’re using Windows, macOS, Linux, or any other operating system with a compatible JVM, this same compiled bytecode can be executed without any changes. This ability to write the code once and run it anywhere demonstrates the principle of “Write Once, Run Anywhere” in Java.