15.7 擦除的神秘之处

package chapter15._7;

import java.util.ArrayList;

public class ErasedTypeEquivalence {

    public static void main(String[] args) {
        Class c1 = new ArrayList<String>().getClass();
        Class c2 = new ArrayList<Integer>().getClass();
        System.out.println(c1 == c2);
    }

}

输出

true

---

package chapter15._7;

import java.util.*;

class Frob {}
class Fnorkle {}
class Quark<Q> {}
class Partiicle<POSITION, MOMENTUM> {}

public class LostInformation {

    public static void main(String[] args) {
        List<Frob> list = new ArrayList<Frob>();
        Map<Frob, Fnorkle> map = new HashMap<Frob, Fnorkle>();
        Quark<Fnorkle> quark = new Quark<Fnorkle>();
        Partiicle<Long, Double> p = new Partiicle<Long, Double>();

        System.out.println(Arrays.toString(list.getClass().getTypeParameters()));
        System.out.println(Arrays.toString(map.getClass().getTypeParameters()));
        System.out.println(Arrays.toString(quark.getClass().getTypeParameters()));
        System.out.println(Arrays.toString(p.getClass().getTypeParameters()));
    }

}

输出

[E]
[K, V]
[Q]
[POSITION, MOMENTUM]