Java - 1st Java Program Explanation - Program Syntax Tutorial

// Java 1st Hello World Program

public class FirstProgram{

    public static void main(String[] args) {

        System.out.println("Hello World");

/* This Line will Print Hello World */

   }

}

Run Program

Java FirstProgram Explanation

• Every line of code must be written inside class. In our case class name is FirstProgram
• Class Should Always start with Capital letter.
• Java File name and Class name should be same. In our case file name FirstProgram.java should match with class name FirstProgram.
• Java is case-sensitive , FirstProgram and firstprogram has different meaning.

Syntax Explanation

• Class Keyword- It is used to declared a classname in java.For example in below example we use class FirstProgram{…} . So here we declare FirstProgram as a classname.
• Public keyword- It is access modifier. Which means it is publicly (visible) to all.
• Static keyword- If we declare any method as static, then it will automatically invoke by JVM. Therefore main method is automatically invoke by JVM. Because it is static method.
• void is the return type of the method. It means it doesn't return any value.
• Main Method

Every java program has main() method.Which is entry point of a program.

• String[] args

• System.out.println()

It is used to print message. As shown in example we have printed  “Hello World”.Same as printf in C Programming.

      How Java Program Run?

Compilation:

When we compile Java program using javac tool, java compiler converts the source code (i.e FirstProgram.java) into byte code (FirstProgram.class).