Why final instance class variable in Java?

Question

If instance variable is set final its value can not be changed like

public class Final {

    private final int b;

    Final(int b) {
        this.b = b; 
         


        

Answer 1

When a reference is final, it cannot be linked to any other object.

The values of the object can be changed, so you can add values to the map, but cannot change the object of the map.