public class Container<T> {
private T value;
public <U extends T> void set(U value) {
this.value = value;
}
public T get() {
return value;
}
}
// 使用:
Container<Number> c = new Container<>();
c.set(42); // line 1
c.set(3.14); // line 2
Integer i = c.get(); // line 3

