When is it appropriate to use blank final variables?

Question

I was looking at another question about final variables and noticed that you can declare final variables without initializing them (a blank final variable). Is there a reaso

Answer 1

The final property of class must have a value assigned before object is created. So the last point where you can assign value to them is constructor.

This is used often for immutable objects.

 public class Foo {

  private final Bar bar;

  public Foo(Bar bar) {
    this.bar = bar;
  }

  public Bar getBar() {
   return new Bar(bar);
 } 
}

What wiki says about it

Defensive copying.