Java @Override: Usage Guide

In Java, @Override is an annotation used to indicate that a method is overriding a method from a parent class or implementing a method from an interface. It helps developers in checking if a method is correctly overriding a method from a parent class or interface.

The use of the @Override annotation helps remind the compiler to check if the signature of a method (method name, parameter list, and return type) matches that of a method in the superclass or interface. If there is a mismatch, the compiler will throw an error, thereby preventing potential mistakes.

Here is how to use the @Override annotation:

1. When a method is marked as @Override, it must exist in the parent class, otherwise it will result in a compilation error.
2. The method signature must be identical to the method being overridden, including the method name, parameter list, and return type.
3. This can only be used for methods, not for other members such as properties or constructors.
4. The @Override annotation is just a marker that can be optionally used, but it is recommended to use it as it can enhance the readability and maintainability of the code.

The example code is as follows:

class SuperClass {
    public void printMessage() {
        System.out.println("Hello, World!");
    }
}

class SubClass extends SuperClass {
    @Override
    public void printMessage() {
        System.out.println("Hello, Java!");
    }
}

In the above example, the SubClass class utilizes the @Override annotation to override the printMessage method from the parent class SuperClass. Without using the @Override annotation, the compiler would not detect this error.