In Java, an annotation is any text preceded by the @ character. Following are a few fairly common annotations.

@Override
@Remote
@Stateless

As a practice example, this code contains two identical methods (myMethod). If the @Override annotion is not used, myMethod in the child class would behave as the main method. Using @Override instructs the compiler to use myMethod in the child class as a sub-method.

public class ParentClass {

    public void myMethod() {
        System.out.println("Parent method");
    }
}

public class ChildClass extends ParentClass {

    @Override
    public void myMethod() {
        System.out.println("Child method");
    }
}

Sometimes, annotations are used instead of comments, since annotation can instruct the compiler to do something, where comments have not impact on the compiler.

// John Doe
// Jane Doe

An annotation can contain key value pairs.

@People(
   id = "1",
   name = "John Doe"
)

The same annotation can be used more than once.

@People(name = "John Doe")
@People(name = "Jane Doe")