What's @Override for in Java?

public class Animal {
    public void eat() {
        System.out.println("I eat like a generic Animal.");
    }
}

public class Wolf extends Animal {
    @Override
    public void eat() {
        System.out.println("I eat like a Wolf!");
    }
}

Does @Override actually have some functionality or is it just kinda like a comment?

Solution

From the Java Tutorials on annotations:

@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.

Let's take a look at the example given in the Java Language specifications, 9.6.1.4 Override. Let's say you want to override a method, equals in that case, but you wrote:

public boolean equals(Foo that) { ... }

instead of:

public boolean equals(Object that) { ... }

While this code is legal, annotating the equals method declaration with @Override would trigger a compile time error because you're in fact not overriding it, you're overloading it. This can cause nasty bugs and the Override annotation type helps at detecting them early.