What is the meaning of bytecode in java?

In this java tutorial, our focus will be on understanding:

• What is bytecode in java?
• How is bytecode helpful in making java platform independent?
• why bytecode is needed?
• bytecode in java example demonstrating creation of java bytecode for better understanding of concept.

You can also refer the video tutorial on what is bytecode in java?

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Bytecode plays a vital role in java programming laguage.

 

Here we will learn about bytecode in java, see bytecode in java definition, bytecode in java example and understand why bytecode is needed?

 

WHAT IS BYTECODE IN JAVA?

Bytecode is a specialized set of instructions that is read, verified and understood by JVM or Java Virtual Machine.

 

When a java source code is compiled then it is converted into bytecode which could be executed on same system or ported to other system having JVM and executed.

Bytecode and JVM together helps in making java platform independent.

See the below diagram to understand the above statement:

 

• If you go to the java classpath, where your .class files are stored and try to open the file you can see the generated bytecode for your java code.
• Even though you will not be able to understand anything that is written in the .class file but you will get the feel of how bytecode present in .class file looks like.
• But remember, JVM will easily understand what is written in .class file.

 

Why bytecode is needed?

Bytecode helps in following ways:

• Since java code is converted to bytecode which can be easily interpreted by any system that has JVM, so it helps in making java portable programming language.
• Bytecode and JVM together helps make java - platform independent, a very popular feature of java program.

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Lets see a practical view for above example to understand creation of .class file and bytecode in java:

 

BYTECODE IN JAVA EXAMPLE

We are going to write a simple java program with file name - Hello.java

Source: Hello.java

package basic;

public class HelloJava {

	public static void main(String[] args) {
		System.out.println("Hello World");
		System.out.println("Hello Java");
		System.out.println("Hello Learning");

	}

}

Compile the above code. I have compiled and run it from Eclipse.

To compile and run from command prompt, use below commands:

• Compile: javac HelloJava.java
• Run: java HelloJava

A Hello.class file will be created at the classpath similar to the one shown in below image. 

 

If you open the above HelloJava.class file with the help of notepad, you will see the bytecode in java as shown below:

 

BYTECODE IN JAVA Hello.class file

Given below is the content of the Hello.class file that contains bytecode in java definition.

Êþº¾   4 & 
 basic/HelloJava 
 java/lang/Object
 

Above content can be read, verified and interpreted by JVM present in the system.

 

This is all about bytecode in java or bytecode in java definition.

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You can visit given links for:

• Complete java tutorial: Free Java tutorial
• Java Programs: Java Practice Programs
• Java MCQS: Java Practice MCQs
• Why java is platform independent?