使用“this”调用超类方法的子类

Question

If superclass has a method that uses the keyword " this " and subclass call this method, would superclass method using " this " refer to the subclass object?

Answer 1

No, this will always referes to the instance of the class in which we are using it.

If we use this in parent class it will always return parent class instance.

If you want to use this of child class in parent class method,Please override the method of parent class.

Answer 2

this always refer to the self object. ie., If a child uses this reference, it points to child. If a parent uses this , it points to parent.

If this cannot find a reference to what is needed in the self, then it looks for the reference in parent.

I doubt your confusion is coming from method overriding, where a parent may call a method with this , but method in child is executed. This is because, the object which gets created in always of the child. So this points to child in that case.

Put it simply, this points to the instance of class which was instantiated. If that instance does not contain the referred entity, then lookup is done on parent (if any)

Answer 3

The keyword this in a class will always refer to the object.

I have crated few sample classes for better understanding.

Parent Class

public class TestClass{
    public void func(){
        this.cFunc();
        System.out.println("In Parent");
    }

    public void cFunc(){
        System.out.println("cFunc in parent");
    }
}

Child Class

public class TestClassChild extends TestClass{
    public void cFunc(){
        System.out.println("cFunc in child");
    }
}

Cases

1) Child Object accessed using Child Class reference

TestClassChild tc = new TestClassChild();
tc.func();

Output

TestClass t = new TestClassChild();
t.func();

2) Child Object accessed using Parent Class reference

TestClass t = new TestClassChild(); t.func();

Output

 cFunc in child - Irrespective if it was referenced by parent still child method got called. In Parent

3) Parent Object accessed using Parent Class reference

 TestClass tp = new TestClass(); tp.func();

Output

 cFunc in parent - Parent function got called. In Parent

Hope the below examples will make things clear for you.