Q 18 - ByteCode

[HARSHITH-MV]

What is bytecode and how is it executed?

[AmjustGettingStarted]

What is Bytecode and How Is It Executed?

Bytecode is an intermediate, platform-independent code generated after Java source code is compiled. It's designed to be understood and executed by the Java Virtual Machine (JVM), not directly by hardware.

Steps of Execution

1. Compilation

   • Java source code (.java files) is compiled using the javac compiler.
   • Output: .class files containing bytecode.

2. Execution by JVM

   • The JVM reads the bytecode and translates it into native machine code.
   • This translation happens via:
     • Interpreter: Executes bytecode line by line.
     • JIT (Just-In-Time) Compiler: Converts bytecode into native code on the fly to boost performance.

Example

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

Compiling this with javac Hello.java produces a Hello.class file. This .class file contains bytecode that can be executed on any platform with a JVM.

Key Characteristics

• Platform Independent
  Bytecode can run anywhere a JVM is present—Windows, Linux, macOS, etc.

• Secure and Optimized
  Bytecode helps Java enforce access control and sandboxing, supporting secure application development.

• Portable and Efficient
  Developers write code once, and bytecode ensures it runs consistently across different environments.

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