擦除的补偿

擦除丢失了在泛型代码中执行某些操作的能力，任何在运行时需要知道确切类型信息的操作都将无法进行，通过类型标签来对擦除进行补偿。

package com.cognizant.ch15;

class Building {
}

class House extends Building {
}

public class ClassTypeCapture<T> {
 Class<T> kind;

 public ClassTypeCapture(Class<T> kind) {
  this.kind = kind;
 }

 public boolean f(Object obj) {
  return kind.isInstance(obj);
 }

 public static void main(String[] args) {
  ClassTypeCapture<Building> ctt = new ClassTypeCapture<Building>(
    Building.class);
  System.out.println(ctt.f(new House()));
  System.out.println(ctt.f(new Building()));
 }
}
output:

true
true