When should I use “this” in a class?

Question

I know that this refers to a current object. But I do not know when I really need to use it. For example, will be there any difference if I use x i

Answer 1

this is a reference to the current object. It is used in the constructor to distinguish between the local and the current class variable which have the same name. e.g.:

public class circle {
    int x;
    circle(int x){
        this.x =x;
        //class variable =local variable 
    }
} 

this can also be use to call one constructor from another constructor. e.g.:

public class circle {
    int x;

    circle() { 
        this(1);
    }

    circle(int x) {
        this.x = x; 
    }
}