Thread: Final Keyword In Java

I'm not sure where the final keyword comes in handy when used on method arguments.

If we ignore the use of anonymous classes, readability, and intent statement, it appears nearly worthless to me.

public void testNullify() {
    Collection<Integer> c  = new ArrayList<Integer>();      
    nullify(c);
    assertNotNull(c);       
    final Collection<Integer> c1 = c;
    assertTrue(c1.equals(c));
    change(c);
    assertTrue(c1.equals(c));
}
 
private void change(Collection<Integer> c) {
    c = new ArrayList<Integer>();
}
 
public void nullify(Collection<?> t) {
    t = null;
}

Enforcing the consistency of some data is not as robust as it appears.

If the parameter is a primitive, it has no effect because it is supplied to the method as a value and modifying it has no effect beyond the scope.

If we pass a parameter by reference, the reference is a local variable, and changing the reference from within the method, as described in the scaler topic, has no effect outside of the method scope.

Consider the following simple test example. This test passes despite the fact that the method changes the value of the reference passed to it, which has no effect.

its immutable in the current scope. If you find that you want to change the value of it in a sub-method, then you've probably already taken a wrong turn somewhere.

You're right in pointing out that the final keyword, when applied to method parameters in Java, can sometimes feel like it's not doing much, especially when dealing with reference types. Let’s break it down:

What Does final on Method Parameters Do?
When you use final on a method argument, you're saying that the reference itself cannot be reassigned within the method. It does not make the object that the reference points to immutable—only the reference variable is protected from being reassigned.

This is important because, without final, you can change the reference to point to another object inside the method. With final, you cannot reassign the reference variable to a new object or null within the method, but you can still mutate the object that the reference points to (if it's mutable).