equals():
=========

package io.ashokit.pack1;

import java.util.Objects;

class A{
	String s1;
	
	A(String s1){
		this.s1 = s1;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		A other = (A) obj;
		return Objects.equals(s1, other.s1);
	}
	
	
	
}

public class MainClass {

	public static void main(String[] args) {
		A a1 = new A("Java");
		A a2 = new A("Java");
		
		System.out.println(a1 == a2);
		System.out.println(a1.equals(a2));
		System.out.println("==================");
		
		String s1 = new String("Java");
		String s2 = new String("Java");
		
		System.out.println(s2 == s1);
		System.out.println(s1.equals(s2));
		System.out.println("==================");
		}
}

==========================
-> in general, the equal operator (==) can compare the object's addresses are same or not.
 	if addresses are same ==> == return: true
	otherwise: == return: false
-> equals() can compare the internal content of objects:
	if internal content of both objects are same :
		equals() can return: true
		otherwise: false
-> equals() can be overridden in the strings already.
-> when we can apply equals() on two object of class A (user-defined), 
	in this case, equals() can behave like equal operator.
	because equals() method was not overridden.
-> if we can override the equals() in class A:
	then it will compare with the internal content of two objects of class A.
-> equals() is Object class method.