ain.java file must have public class with name 'Main' You must declared Main class which contains 'main' method, which is entry point of program execution. code example

Example 1: java define main function

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

Example 2: main method java

public class Test {

static void main(String[] args){

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