Within an instance method or a constructor, this is a reference to the current object — the object whose method or constructor is being called. You can refer to any member of the current object from within an instance method or a constructor by using this.
The most common reason for using the this keyword is because a field is shadowed by a method or constructor parameter.
For example, the Point class was written like this
public class Point {
public int x = 0;
public int y = 0;
//constructor
public Point(int a, int b) {
x = a;
y = b;
}
}
but it could have been written like this:
public class Point {
public int x = 0;
public int y = 0;
//constructor
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
Each argument to the constructor shadows one of the object's fields — inside the constructor x is a local copy of the constructor's first argument. To refer to the Point field x, the constructor must use this.x.
You can find good example here(Also they will show the diffrent uses of the "this" keyword) ---> http://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html