Question

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When do you use Java's @Override annotation and why?

My question is very basic why we people use @Override annotation and what is the importance of this annotation?

In Old JDK why it not show as warning, but in latest JDK it required then Why..?

Answer 1

Suppose you have:

public class Foo
{
    public void bar(String x, String y) {}
}

public class Foo2 extends Foo
{
    public void bar(String x, Object y) {}
}

You really meant Foo2.bar to override Foo.bar, but due to a mistake in the signature, it doesn’t. If you use @Override you can get the compiler to detect the fault. It also indicates to any reading the code that this is overriding an existing method or implementing an interface – advising them about current behaviour and the possible impact of renaming the method.

Additionally, your compiler may give you a warning if a method overrides a method without specifying @Override, which means you can detect if someone has added a method with the same signature to a superclass without you being aware of it – you may not want to be overriding the new method, as your existing method may have different semantics. While @Override doesn’t provide a way of “un-overriding” the method, it at least highlights the potential problem.