Core Java

public static void main (string args[]) Explanation

In Java, JVM (Java Virtual Machine) will always look for a specific method signature to start running an application, and that would be public static void main (String args[]).

Here args is an argument of the type String array. String array argument can also be written as String[] args. Though the type of the argument (String array) is fixed, you can still change the name from args to anything.

Also with the introduction of java args, instead of writing String args[], String… args can be used.  Keep learning to know more about each and every keyword.

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

In the above application example, we are using the public static void main. Each word has a different meaning and purpose.

Public

It is an Access Modifier, which defines who can access this Method. Public means that this Method will be accessible by any Class(If other Classes can access this Class.).

Static

Static is a keyword that identifies the class-related thing. It means the given Method or variable is not instance-related but Class related. It can be accessed without creating the instance of a Class.

Void

It is used to define the Return Type of the Method. It defines what the method can return. Void means the Method will not return any value.

main

Main is the name of the Method. This Method name is searched by JVM as a starting point for an application with a particular signature only.

String args[] / String… args

It is the parameter to the main method. The argument name could be anything. You can either use String array (String args[]) or var args variable of String type. Both will work the same way.

Author

74 thoughts

      1. right ,we have developer ,most engineering pass out in first but those student not able to do coding this is different between software developer and english gentleman.

      2. In this platform not a english debata,it is a programming language platform so does not matter english grammer.(some of the english grammer mistake so we will be adjust……)

  1. String args[] : Parameter to main method…

    Please site how to use the main() with values given to parameters (like what the difference would be with (or without) these values).

    1. If u dont use it shows error in execution….that y we r passing infinite arguments in String type…string is one.type of class ….so,first letter is capital

    1. HI,

      This is a standard which needs to follow if we want jvm to search it to execute it. There is no harm in removing this parameter from method but then that method will be treated as other java methods and it will not be directly called by JVM.

    2. The main method will compile successfully but will not run. As it will be treated as any other method.
      Certain standard to be followed for main method

  2. My program still runs if I use other word instead of args in “String[] args”(Parameter to main method). I want to know the reason behind it.

  3. good explanation but give me parameters at the same time explanation. i mean which type of parameters in using java.
    and please give me different meanings Hello and hello in java

  4. Hi,

    I want to know why JVM treats main(String [] args) method as a starting point of program, can anyone tell me the internal functioning of this method, like how it gets execute and what threads are required to execute this method so that JVM can understand this method as the starting point of the program.?

    1. Suppose you are watching a movie and the scene of movie starts from middle of a story and as you continue watching movie, u need to understand the current scene of movie and for that movie makes gives u a starting part of movie in somewhere middle of movie(Gives you information something like” 15years before ” in movie)..by reading this words in movie you get to know the starting of movie…
      So likewise u place you main method anywhere in program(inside class) the JVM will read full code in its language to find main() method and starts acknowledging(executing) the code from main method…
      and if you dont provide main() method in code the JVM will not understand the story of your code will give error…

    1. It is shortcut English grammar that is enough for developers to understand each other so they can write efficient English with minimal words – like good programming style that is less verbose

    1. Hi Vinod,

      Public and static keyword position can be changed. There is no such rule of using public before static. But as void is method return type it should come just before method name which is main in this case. Hence this sequence.
      public static void main
      static public void main.

      Both are same. But as a standard we right as in the first case.

  5. I want list and description of in build classes and their sub classes…like printsteam is class and println() is its method…

  6. Can you please explain…how internally works these SYSOUT statement??
    System.out.println(“args[” +i+ “]:”+args[i] );
    System.out.println(“args[ i ]:”+args[i] );

    1. 1) System -is a class in the java.lang package .

      2) out -is a static member of the System class, and is an instance of java.io.PrintStream .

      3) println -is a method of java.io.PrintStream. This method is overloaded to print message to output destination, which is typically a console or file.

  7. thank u for update ur information
    i have some cofusion in null point exception
    please send me a link of ur site in null point exception

    1. You can write main method without static keyword, there will not be any issue. But it will not work as expected. It will be treated as normal method and in order to execute it you need to call given method explicitly. While static keyword will make this method to be treated as entry point. Hope it clarifies.

  8. why we are using string[] args in pubic static void main(String[] args) why we are not using character array or int array i need elabrate answer

  9. A Java program is a sequence of Java instructions that are executed in a certain order. Since the Java instructions are executed in a certain order, a Java program has a start and an end.

  10. Hi, I already knew the main method is the entry point of the program and makes it execute the program properly but this explanation is really good for adults and kids. Thank you very much. This helped me a lot for public static void main(String[] args). I appreciated it a lot. I am a seven year old kid and I love programming.

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