There are three annotation types that are predefined by the language specification itself: @Deprecated, @Override, and @SuppressWarnings.
@Deprecated—the @Deprecated annotation indicates that the marked element is deprecated and should no longer be used. The compiler generates a warning whenever a program uses a method, class, or field with the @Deprecated annotation. When an element is deprecated, it should also be documented using the Javadoc @deprecated tag, as shown in the following example. The use of the “@” symbol in both Javadoc comments and in annotations is not coincidental—they are related conceptually. Also, note that the Javadoc tag starts with a lowercase “d” and the annotation starts with an uppercase “D”.

   // Javadoc comment follows
    /**
     * @deprecated
     * explanation of why it was deprecated
     */
    @Deprecated
    static void deprecatedMethod() { }
}

@Override—the @Override annotation informs the compiler that the element is meant to override an element declared in a superclass (overriding methods will be discussed in the the lesson titled “Interfaces and Inheritance”).

   // mark method as a superclass method
   // that has been overridden
   @Override 
   int overriddenMethod() { }

While it’s not required to use this annotation when overriding a method, it helps to prevent errors. If a method marked with @Override fails to correctly override a method in one of its superclasses, the compiler generates an error.
@SuppressWarnings—the @SuppressWarnings annotation tells the compiler to suppress specific warnings that it would otherwise generate. In the example below, a deprecated method is used and the compiler would normally generate a warning. In this case, however, the annotation causes the warning to be suppressed.

   // use a deprecated method and tell 
   // compiler not to generate a warning
   @SuppressWarnings("deprecation")
    void useDeprecatedMethod() {
        objectOne.deprecatedMethod(); //deprecation warning - suppressed
    }

Every compiler warning belongs to a category. The Java Language Specification lists two categories: “deprecation” and “unchecked.” The “unchecked” warning can occur when interfacing with legacy code written before the advent of generics (discussed in the lesson titled “Generics”). To suppress more than one category of warnings, use the following syntax:
@SuppressWarnings({“unchecked”, “deprecation”})