The Standard Edition of Java comes with some annotations predefined. You do not need to define them by yourself and you can use them immediately. They allow the compiler to enable some fundamental checking of methods, classes and code.

@Override

This annotation applies to a method and says that this method must override a superclass’ method or implement an abstract superclass’ method definition. If this annotation is used with any other kind of method, the compiler will throw an error.

Concrete superclass

public class Vehicle {
   public void drive() {
        System.out.println("I am driving");
   }
}

class Car extends Vehicle {
    // Fine
    @Override
    public void drive() {
        System.out.prinln("Brrrm, brrm");
    }
}

Abstract class

abstract class Animal  {
   public abstract void makeNoise(); 
}

class Dog extends Animal {
    // Fine
    @Override
    public void makeNoise() {
        System.out.prinln("Woof");
    }
}

Does not work

class Logger1 {
    public void log(String logString) {
        System.out.prinln(logString);
    }
}

class Logger2 {
    // This will throw compile-time error. Logger2 is not a subclass of Logger1. 
    // log method is not overriding anything
    @Override
    public void log(String logString) {
        System.out.println("Log 2" + logString);
    }
}

The main purpose is to catch mistyping, where you think you are overriding a method, but are actually defining a new one.

class Vehicle {
   public void drive() {
        System.out.println("I am driving");
   }
}

class Car extends Vehicle {
    // Compiler error. "dirve" is not the correct method name to override.
    @Override
    public void dirve() {
        System.out.prinln("Brrrm, brrm");
    }
}

Note that the meaning of @Override has changed over time:

• In Java 5, it meant that the annotated method had to override a non-abstract method declared in the superclass chain.
• From Java 6 onward, it is also satisfied if the annotated method implements an abstract method declared in the classes superclass / interface hierarchy.

(This can occasionally cause problems when back-porting code to Java 5.)

@Deprecated

This marks the method as deprecated. There can be several reasons for this:

• the API is flawed and is impractical to fix,
• usage of the API is likely to lead to errors,
• the API has been superseded by another API,