Tutorial

public static void main(String[] args) - Java main method

Updated on November 4, 2022
authorauthor

Pankaj and Andrea Anderson

public static void main(String[] args) - Java main method

Introduction

The Java main method is usually the first method you learn about when you start programming in Java because its the entry point for executing a Java program. The main method can contain code to execute or call other methods, and it can be placed in any class that’s part of a program. More complex programs usually have a class that contains only the main method. The class that contains the main method can have any name, although typically you can just call the class Main.

In the examples that follow, the class that contains the main method is called Test:

Test.java
public class Test {

	public static void main(String[] args){

		System.out.println("Hello, World!");
	
	}
}

In this article you’ll learn what each component of the main method means.

Java Main Method Syntax

The syntax of the main method is always:

public static void main(String[] args){
	// some code
}

You can change only the name of the String array argument. For example, you can change args to myStringArgs. The String array argument can be written as String... args or String args[].

public

The access modifier of the main method needs to be public so that the JRE can access and execute this method. If a method isn’t public, then access is restricted. In the following example code, the main method is missing the public access modifier:

Test.java
public class Test {

	static void main(String[] args){

		System.out.println("Hello, World!");
	
	}
}

When you compile and run the program, the following error occurs because the main method isn’t public and the JRE can’t find it:

  1. javac Test.java
  2. java Test
Output
Error: Main method not found in class Test, please define the `main` method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

static

When the Java program starts, there is no object of the class present. The main method has to be static so that the JVM can load the class into memory and call the main method without creating an instance of the class first. In the following example code, the main method is missing the static modifier:

Test.java
public class Test {

	public void main(String[] args){

		System.out.println("Hello, World!");
	
	}
}

When you compile and run the program, the following error occurs because the main method isn’t static:

  1. javac Test.java
  2. java Test
Output
Error: Main method is not static in class Test, please define the `main` method as: public static void main(String[] args)

void

Every Java method must provide the return type. The Java main method return type is void because it doesn’t return anything. When the main method is finished executing, the Java program terminates, so there is no need for a returned object. In the following example code, the main method attempts to return something when the return type is void:

Test.java
public class Test {

	public static void main(String[] args){
	
		return 0;
	}
}

When you compile the program, the following error occurs because Java doesn’t expect a return value when the return type is void:

  1. javac Test.java
Output
Test.java:5: error: incompatible types: unexpected return value return 0; ^ 1 error

main

The Java main method is always named main. When a Java program starts, it always looks for the main method. The following example code shows a main method renamed to myMain:

Test.java
public class Test {

	public static void myMain(String[] args){

		System.out.println("Hello, World!");
	}
}

When you compile and run the program, the following error occurs because the JRE can’t find the main method in the class:

  1. javac Test.java
  2. java Test
Output
Error: Main method not found in class Test, please define the `main` method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application

String[] args

Java main method accepts a single argument of type String array. Each string in the array is a command line argument. You can use command line arguments to affect the operation of the program, or to pass information to the program, at runtime. The following example code shows how to print the command line arguments that you enter when you run the program:

Test.java
public class Test {

	public static void main(String[] args){

    	for(String s : args){
		System.out.println(s);
    	}
	
    }
}

When you compile the program and then run it with a few command line arguments separated by spaces, the arguments get printed in the terminal:

  1. javac Test.java
  2. java Test 1 2 3 "Testing the main method"
Output
1 2 3 Testing the main method

Conclusion

In this article you learned about each component of the Java main method. Continue your learning with more Java tutorials.

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JournalDev
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March 6, 2022

import java.util.Scanner; public class Main { public static void main (String[] args){ Scanner input= new Scanner(System.in); boolean isOnRepeat=true; while(isOnRepeat){ System.out.println (“play the currentsong”); System.out.println(“do you want to change the song, If so answer yes”); String userInput = input.next(); if(userInput.equals(“yes”)) { isOnRepeat=false; } } System.out.println (“play the next song”); } }

- Jeyaharini

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    December 8, 2021

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    - RK

      JournalDev
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      October 18, 2021

      Arrays in java are all supposed to have a fixed size, but the array of strings that’s passed to main (String[] args) doesn’t. Is this a hard-coded exception to the rule? Are there any other such examples?

      - Jackson

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        - Ackeem

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          October 28, 2020

          Help me determine the output for the given code snippet: public class App { public static void main( String[] args ) { for(;;) { System.out.println(“Hi”); } } }

          - Dia

            JournalDev
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            August 26, 2020

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            - nhlanhla

              JournalDev
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              April 28, 2020

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              - kim ka

                JournalDev
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                March 11, 2020

                My teacher writes as public static void main(String St[]) and it is executed. My question is that (1) what are the maximum possibilities to write in different string names? (2) Why we need to use array in different names? (3) What is the purpose of using different name for String?

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                  public class Main { private String isbn, author, title, publisher, publishdate; private int price; private String borrower,category; private int payment; private int numberofdays; public Main(){ isbn=“unassigned”; author=“unnasigned”; title=“unnasigned”; publisher=“unnasigned”; publishdate=“unnasigned”; price= 0; } public void setNumberofdays(int nd){ numberofdays = nd; } public void setBorrower(String b){ category = b; } public void setCategory (String c){ category= c; } public void setBookTitle(String t){ title = t; } public void setPublisher(String p){ publisher = p; } public void setAuthor(String a){ author = a; } public void setPublishDate(String pd){ publishdate = pd; } public void setpayment(int pm){ payment = pm; } public void setISBN(String i){ isbn = i; } public void setPrice(int p){ price = p; } public void setPayment (int nd){ payment = nd*5; } public int getNumberofdays(){ return numberofdays; } public String getAuthor(){ return author; } public String getISBN(){ return isbn; } public String getBorrower(){ return borrower; } public String getCategory(){ return category; } public String getBookTitle(){ return title; } public int getpayment(){ return payment; } public String getPublisher(){ return publisher; } public String getPublishDate(){ return publishdate; } public int getPrice(){ return price; } public int getPayment(){ return payment; } } Why my code is not working??

                  - Ricardo

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                    December 12, 2019

                    are these correct? public static main(String[ ] args) public static void[ ] main(String[ ] args) public int static main(String[ ] args) public static void mian (String args)

                    - yon

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