shadowed variables

[Thirumalai Muthu]

[1] class Foo{
[2] Bar myBar= new Bar();
[3] void changeIt(Bar myBar)
[4] {
[5] myBar.barNum=99;
[6] System.out.println("myBar.barNum in changeIt is " + myBar.barNum);
[7] myBar=new Bar();
[8] myBar.barNum=420;
[9] System.out.println("myBar.barNum in changeIt is now" + myBar.barNum);
[10] )
[11] public static void main(String [] args) {
[12] Foo f=new Foo();
[13] System.out.println("f.myBar.barNum is " + f.myBar.barNum);
[14] f.changeIt(f.myBar);
[15] System.out.println("f.myBar.barNum after changeIt is " + f.myBar.barNum);
[16] }
[17] }

class Bar{
int barNum=28;
}

Can anyone Please explain the lines [6],[9],[13],[14] and [15].Thank you.
[ October 09, 2007: Message edited by: Thirumalai Muthu ]

[Vishal Arhatia]

Hi,

Before line 9 all instance variables gets initialized.

So, at line 9 it prints 28.

When it calls f.changeIt(f.myBar) at line 14, it is passing the same the value of address where reference for object initialized at line 2 is stored.

According to rules when modification of any value of object happens then it gets stored at same address, but if new object is created then the result is stored at different address.

So,
Line 6 prints the modified value 99.
Line 9 will print 420 for the new myBar object.

And line 15 will print 99 because the modified value of passed myBar object has changed to 99 at line 5.

Hope this is clear.

[Krithika Srinath]

Before line 9 all instance variables gets initialized.

So, at line 9 it prints 28.

In the above sentence it should be line 13 and not 9... rest of the explanation seems fine.

[Thirumalai Muthu]

Thank you Vishal and krithika.I understood.