java中，到底overwrite和override有什么区别

代码如下：
//所有的Override都可以去掉，效果一样！！！
public class Test {

public interface I{
int work();
}

public class A implements I{
@Override
public int work() {
System.out.println("A works...");
return 0;
}
}

public class B extends A{

}

public class C extends A{
@Override
public int work(){
System.out.println("C works...");
return 0;
}
}

public class D extends A{
public int work(){
System.out.println("D works...");
return 0;
}
}

public int work(){
A b = new B();
b.work();
System.out.println("----");
A c = new C();
c.work();
System.out.println("----");
A d = new D();
d.work();
return 0;
}

public static void main(String[] args){
BaseTest test = new BaseTest();
test.work();
}

}