Use of final local variables in java [duplicate]

Answer 1

You might use final keyword for readability and ensuring it is not modified or in anonymous classes like here:

    final String s = "hi";
    new Thread(new Runnable() {
        @Override
        public void run() {
            // can use s variable here
        }
    }).start();

Answer 2

Yes, the usability is :- local final variable are accessible by the method inner class. Since local variables live on the stack and exist only for lifetime of the method but Inner class object may live longer so inner class can't access any non final local variable. But once the variable is final then the inner class sure that the value won't change so it keep a private copy of the final local variable for use.

Answer 3

final local variables may be accessed from anonymous inner subclasses, whereas non final local variables may not.

Answer 4

yes there is, a small expample where we could normally use it -

Snippet:

final Boolean data = Boolean.TRUE;
button.addListener(SWT.Selection, new Listener() {
    public void handleEvent(Event event) {
        if (data ) {
                     ....
                }
        }
});

Its a example of usage with anonymous inner classes. If you want to use your local variable inside inner calss, you have to make final.

Answer 5

Firstly, the part about variables being "overridden" - final has two very different meanings. For classes and methods, it's about inheritance; for variables it's about being read-only.

There's one important "feature" of final local variables: they can be used in local (typically anonymous) inner classes. Non-final local variables can't be. That's the primary use of final for local variables, in my experience.

public void foo() {
    final String x = "hello";
    String y = "there";

    Runnable runnable = new Runnable() {
        @Override public void run() {
            System.out.println(x); // This is valid
            System.out.println(y); // This is not
        }
    };
    runnable.run();
}

Note that as a matter of style, some people like to use final even when they're not capturing the variable in a local inner class. I'd certainly be comfortable with final being the default, but a different modifier for "non-final", but I find that adding the modifier explicitly everywhere is too distracting.

Answer 6

Use of final local variables in java

final fields, parameters, and local variables are read-only(means the object's identity, not its state).