Java1.7以上では、abstractメソッドにもアノテーションが適用される ref: http://qiita.com/kamatama_41/items/950ac13f1864530ae3f3

file0.java

public abstract class Parent {
    public abstract Number someMethod();
}

public class Child extends Parent {
    @Override
    @Sample
    public Integer someMethod() {
        return 1;
    }
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Sample {
}

public class CheckHasSampleAnnotation {
    public static void main(String[] args) {
        for (Method method : Child.class.getMethods()) {
            Sample annotation = method.getAnnotation(Sample.class);
            if(annotation != null) {
                System.out.println("----- [" + method + "] has @Sample. -----");
            } else {
                System.out.println("[" + method + "] doesn't have @Sample.");
            }
        }
    }
}

file1.txt

----- [public java.lang.Integer Child.someMethod()] has @Sample. -----
[public java.lang.Number Child.someMethod()] doesn't have @Sample.
[public final void java.lang.Object.wait() throws java.lang.InterruptedException] doesn't have @Sample.
[public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException] doesn't have @Sample.
[public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException] doesn't have @Sample.
[public boolean java.lang.Object.equals(java.lang.Object)] doesn't have @Sample.
[public java.lang.String java.lang.Object.toString()] doesn't have @Sample.
[public native int java.lang.Object.hashCode()] doesn't have @Sample.
[public final native java.lang.Class java.lang.Object.getClass()] doesn't have @Sample.
[public final native void java.lang.Object.notify()] doesn't have @Sample.
[public final native void java.lang.Object.notifyAll()] doesn't have @Sample.

file2.txt

----- [public java.lang.Integer Child.someMethod()] has @Sample. -----
----- [public java.lang.Number Child.someMethod()] has @Sample. -----
[public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException] doesn't have @Sample.
[public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException] doesn't have @Sample.
[public final void java.lang.Object.wait() throws java.lang.InterruptedException] doesn't have @Sample.
[public boolean java.lang.Object.equals(java.lang.Object)] doesn't have @Sample.
[public java.lang.String java.lang.Object.toString()] doesn't have @Sample.
[public native int java.lang.Object.hashCode()] doesn't have @Sample.
[public final native java.lang.Class java.lang.Object.getClass()] doesn't have @Sample.
[public final native void java.lang.Object.notify()] doesn't have @Sample.
[public final native void java.lang.Object.notifyAll()] doesn't have @Sample.