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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..?
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@Override @Override annotation informs the compiler that the element is meant to override an element declared in a superclass. Overriding methods will be discussed in Interfaces and Inheritance. While it is not required to use this annotation when overriding a method, it helps to prevent errors.
The @Override annotation indicates that the child class method is over-writing its base class method. It extracts a warning from the compiler if the annotated method doesn't actually override anything. It can improve the readability of the source code.
The @Override annotation denotes that the child class method overrides the base class method. For two reasons, the @Override annotation is useful. If the annotated method does not actually override anything, the compiler issues a warning.
@Override means you are overriding the base class method. In java6, it also mean you are implementing a method from an interface. It protects you from typos when you think are overriding a method but you mistyped something.
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.
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Just to make sure at compile time that we are really overriding the method, also adds good amount to the readability of code
@Override is there since JDK 1.5, so you might get warning in prior
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