String str = testMap.get(0);
        str = "222";
        Log.e("ttttttest","testMap.get(0)-第四次->  "+testMap.get(0));

在HashMap的外部，更改存放在HashMap裡的物件的屬性值，這個時候HashMap裡的物件對應的值會改變嗎？如果存放在Map的Value的型別是String類呢？ 這裡來驗證一下，首先定義一個Value值為String的Map testMap，一個Value值為Person的的Map testPersonMap；
 然後編寫Person類，person 有一個name屬性。

private Map<Integer, String> testMap = new HashMap<Integer, String>();
private HashMap testPersonMap = new HashMap<Integer, Persion>();
 

    public class Persion {
        private String name;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }

定義兩個String變數string1和string2 放入testMap，這個時候，打印出來，是我們放入時的值沒有錯。

        String string1 = "abc";
        String string2 = "xyz";
        testMap.put(0,String1);
        testMap.put(1,string2);

        Log.e("ttttttest","testMap.get(0)-->  "+testMap.get(0));
        Log.e("ttttttest","testMap.get(1)-->  "+testMap.get(1));
 

這個時候更改string1的值，列印map裡的string1，

        String1 = "111";
        Log.e("ttttttest","testMap.get(0)-第二次->  "+testMap.get(0));

將更改後的string1放入map 列印

        testMap.put(0,String1);
        Log.e("ttttttest","testMap.get(0)-第三次->  "+testMap.get(0));

取出對應位置的string 更改後列印： String str = testMap.get(0); str = "222"; Log.e("ttttttest","testMap.get(0)-第四次-> "+testMap.get(0));將String換成Person類來驗證

        Persion persion1 = new Persion();

        persion1.setName("zhangsan");
        Persion persion2 = new Persion();
        persion2.setName("lisi");
        testPersonMap.put(0,persion1);
        testPersonMap.put(1,persion2);
        Log.e("ttttttest","testPersonMap.get(0)-->  "+((Persion)testPersonMap.get(0)).getName());
        Log.e("ttttttest","testPersonMap.get(1)-->  "+((Persion)testPersonMap.get(1)).getName());
        persion1.setName("wangwu");
        Log.e("ttttttest","testPersonMap.get(0)-第二次->  "+((Persion)testPersonMap.get(0)).getName());
        testPersonMap.put(0,persion1);
        Log.e("ttttttest","testPersonMap.get(0)-第三次->  "+((Persion)testPersonMap.get(0)).getName());

        Persion persion = (Persion)testPersonMap.get(0);
        persion.setName("zhaoliu");

Log.e("ttttttest","testPersonMap.get(0)-第四次-> "+((Persion)testPersonMap.get(0)).getName());

可以看出，對於普通的類來說，Map中存放的只是物件的引用，我們不管是在Map外更改物件的屬性，還是將物件從Map中取出來更改物件，map中存放的物件都會改變。 String str = testMap.get(0); str = "222"; Log.e("ttttttest","testMap.get(0)-第四次-> "+testMap.get(0));