老兄，你測試過你的輸出嗎？ 解釋的沒錯，但你的舉例有問題  回復(fù)  更多評論
  

舉例如下：
//Map<String, String> map = new IdentityHashMap<String, String>();
Map<String, String> map = new HashMap<String, String>();
map.put(new String("luojc"), "luojc");
map.put("luojc","luojc");
System.out.println(map.size());  回復(fù)  更多評論
  

最直接的代碼：
public static void main(String[] args) {
String st1 = new String("luojc");
String st2 = new String("luojc");
Map<String, String> map = new IdentityHashMap<String, String>();
//Map<String, String> map = new HashMap<String, String>();
map.put(st1, "luojc");
map.put(st2,"luojc");
System.out.println(map.size());
System.out.println(st1==st2);
System.out.println(st1.equals(st2));
Set<Entry<String, String>> set = map.entrySet();
for (Entry<String, String> entry : set) {
System.out.println(entry);
}
}  回復(fù)  更多評論
  

@呵呵
朋友，你看到了“Pet中的equals中只要name相等, 就算這兩個pet對象相等. ”這句話了嗎，需要自己重寫equals方法的。  回復(fù)  更多評論
  

package com.map;

import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.Map;

public class IdentityHashMapTest {

public static void main(String[] args) {

Pet p1 = new Pet("eric");
Pet p2 = new Pet("eric");

Map<Pet, String> hashMap = new HashMap<Pet, String>();
hashMap.put(p1, "eric2");
hashMap.put(p2, "hello2");
System.out.println("hashMap size = " + hashMap.size());

Map<Pet, String> map = new IdentityHashMap<Pet, String>();
map.put(p1, "eric1");
map.put(p2, "hello1");
System.out.println("size = " + map.size());

String str1 = new String("eric");
String str2 = new String("eric");

Map<String, String> hashMap2 = new HashMap<String, String>();
hashMap2.put(str1, "eric2");
hashMap2.put(str2, "hello2");
System.out.println("hashMap size = " + hashMap2.size());

Map<String, String> map2 = new IdentityHashMap<String, String>();
map2.put(str1, "eric1");
map2.put(str2, "hello1");
System.out.println("size = " + map2.size());
}
}

class Pet {
String name;

Pet(String name) {
this.name = name;
}
}
  回復(fù)  更多評論