Final static can be changed?

Question

I wrote my code but now i am trying to change to see what is happening.

In the object class field,

static final String msg="here";

And in the same object, in a methot

public void givemessage(int no)
{
    System.out.println("look.");       
    System.out.println(msg);
}

here it gives "here" when i call from main. But

public void names(String[] names)
{
    String msg=" - ";
    System.out.println(msg);
}

Here when i call from main it gives -, not "here" BUt it was final static. Why did it change and why is there no compile error? Or i misunderstood all java?

The local variable in your `names` method hides the static variable. — assylias, Jul 18 '13 at 10:13

score 8 · Answer 1 · answered Jul 18 '13 at 10:12

8

You are using two different variables, the class variable is immutable (final) but the local one is not, they have the same name but they are not the same.

If you want to verify this, put in your main method something like MyClassName.msg="-" and you'll see the compiler will complain.

answered Jul 18 '13 at 10:12

morgano

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2

immutable != final. They are two different concepts. In fact, the String class is an immutable class. Please read here for further explanation http://stackoverflow.com/a/8798424/2542027 – Multithreader Jul 18 '13 at 10:23

score 4 · Answer 2 · answered Jul 18 '13 at 10:15

4

This is called shadowing... the String which is passed to System.out.println is the one you defined within your names method as it has a tighter scope as the one on class level. Check this out http://en.wikipedia.org/wiki/Variable_shadowing

answered Jul 18 '13 at 10:15

Korgen

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i wouldn't agree with the term shadowing, since you can still access both variables – Philipp Sander Jul 18 '13 at 10:23

score 2 · Answer 3 · answered Jul 18 '13 at 10:13

2

msg is a local variable in the names method. It doesnt change the variable at class level.

answered Jul 18 '13 at 10:13

Reimeus

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Philipp Sander · Answer 4 · 2013-07-18T10:21:23.677

1

it did not change.

in this snippet, your accessing the local variable.

public void names(String[] names)
{
    String msg=" - ";
    System.out.println(msg);
}

if you want to access the static field:

System.out.println(ClassName.msg);

edited Jul 18 '13 at 10:21

answered Jul 18 '13 at 10:14

Philipp Sander

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score 1 · Answer 5 · answered Jul 18 '13 at 10:14

1

You are defining a local variable named msg inside the names() method . It is not the same as the static final class method. The local variable inside the method hides the class variable.

answered Jul 18 '13 at 10:14

AllTooSir

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score 1 · Answer 6 · answered Jul 18 '13 at 10:15

1

It did not change. You've "hidden" your static final member behind the local variable. The static final variable still has the old value - you can access it using XXX.msg, where XXX is the name of your class.

answered Jul 18 '13 at 10:15

mthmulders

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score 1 · Answer 7 · answered Jul 18 '13 at 10:27

1

String msg=" - "; is a local variable stored in stack whereas static final String msg="here"; is a class level variable stored in permgen space till java 6(stored in heap in java7). In nutshell you are referring two different variables here

answered Jul 18 '13 at 10:27

M Sach

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Final static can be changed?

7 Answers7