Please Explain me the logic Why I am get the Error Message for the Following Code ?

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Java

package com.contruct;

class Example{
	   //I did not define any constructor here
	   public void disp()
	   {
	      System.out.println("disp method of Example class");
	   }
//	   public static void main(String args[]){
	      Example obj2 = new Example();
//	      obj2.disp();
	   
	}

Error is
Error: Main method not found in class com.contruct.Example, please define the main method as:
public static void main(String[] args)
or a JavaFX application class must extend javafx.application.Application

I understant ,if i remove comment ,code will run fine ,but I want to understand the logic ,Why Its Showing compilation Error