Shadowing Variable

[Esha Naidu]

Hi..
Can any one Help me out in clearing the concept of shadowing variable..

[Christophe Verré]

If I remember, it could be like a local variable which has the same name as an instance variable.

public class MyClass {
 private String name;
 
 public void doSomething() {
   String name = "hello";
   ...
 }
}

"name" in doSomething is shadowing the instance "name".

[Manfred Klug]

Another example is shadowing instance variables of a parent class.

class Super {
    int x = 5;
}
 
public class Test extends Super {
    int x = 7;
 
    public void doIt() {
        System.out.println(x);
        System.out.println(super.x);
    }
 
    public static void main(String... args) {
        new Test().doIt();
    }
}

[Esha Naidu]

Hi
Thanku for the replies
Below is code from K&B book
i thought the answer could be 28 99 420 28
but the answer is 28 99 420 99 how it is taking 99 instead of 28 can anyone expalin me clearly..
how the shadowing variable concept is involved here.
Thanks in advance

  
 class Bar {
int barNum = 28;
}
class Foo {
Bar myBar = new Bar();
void changeIt(Bar myBar) {
myBar.barNum = 99;
System.out.println("myBar.barNum in changeIt is " + myBar.barNum);
myBar = new Bar();
myBar.barNum = 420;
System.out.println("myBar.barNum in changeIt is now " + myBar.barNum);
}
public static void main (String [] args) {
Foo f = new Foo();
System.out.println("f.myBar.barNum is " + f.myBar.barNum);
f.changeIt(f.myBar);
System.out.println("f.myBar.barNum after changeIt is "
+ f.myBar.barNum);
}
} 

[kathir vel]

changeIt() is passing the refference of Bar object.So its(passed obect's state) state is changed to 99.Then ,new bar object is assigend to this local refferece variable.Making changes (assigning 420)in this new bar object's state won't affect the called refference Object's state.So after completion of changeIt() method ,Bar object is barNum value is 99.

[Burkhard Hassel]

Esha NS, see this:
http://www.javaranch.com/name.jsp




and change your user name please.


using the code tag on code that hasn't any indentations is pretty useless.

Same code indented:

class Bar {
int barNum = 28;
}
 
class Foo {
Bar myBar = new Bar();
 
void changeIt(Bar myBar) {
myBar.barNum = 99;
System.out.println("myBar.barNum in changeIt is " + myBar.barNum);
myBar = new Bar();
myBar.barNum = 420;
System.out.println("myBar.barNum in changeIt is now " + myBar.barNum);
}
 
public static void main (String [] args) {
Foo f = new Foo();
System.out.println("f.myBar.barNum is " + f.myBar.barNum);
f.changeIt(f.myBar);
System.out.println("f.myBar.barNum after changeIt is "
+ f.myBar.barNum);
}
}

Yours,
Bu.