コンビネーションモードと汎用モード
9165 ワード
package p1;
public class B {
public static void main(String[] args) {
Holder1<? extends Fruit> h1 = new Holder1<Apple>();
h1.set(new Fruit()); //
Fruit f1 = h1.get();
Holder1<? super Fruit> h2 = new Holder1<Fruit>();
h2.set(new Apple());
h2.get(); // Object
Holder1<Apple> h3 = new Holder1<Apple>();
h3.set(new Apple());
h3.get();
Holder1<Orange> h4 = new Holder1<Orange>();
h4.set(new Orange());
h4.get();
Holder2 h5 = new Holder2();
h5.set(new Apple());
h5.get();
}
//
class Holder1<T> {
private T value;
public void set(T val) {
value = val;
}
public T get() {
return value;
}
}
//
class Holder2 {
private Fruit value;
public void set(Fruit val) {
value = val;
}
// (value Fruit )
public Fruit get() {
return value;
}
}
class Fruit {
}
class Apple extends Fruit {
}
class Orange extends Fruit {
}
組み合わせモードと汎用モード、それぞれ千秋があって、いっしょに討論することを歓迎します