TreeMap中添加key-value，要求key必须是由同一个类创建的对象

1. Set keySet()：返回所有key构成的Set集合
2. ** Collection values()：返回所有value构成的Collection集合**
3. ** Set entrySet()：返回所有key-value对构成的Set集合**

public class TreeMapTest {

//向TreeMap中添加key-value，要求key必须是由同一个类创建的对象
//因为要按照key进行排序：自然排序 、定制排序
//自然排序
@Test
public void test1(){
    TreeMap map = new TreeMap();
    User u1 = new User("Tom",23);
    User u2 = new User("Jerry",32);
    User u3 = new User("Jack",20);
    User u4 = new User("Rose",18);

    map.put(u1,98);
    map.put(u2,89);
    map.put(u3,76);
    map.put(u4,100);

    Set entrySet = map.entrySet();
    Iterator iterator1 = entrySet.iterator();
    while (iterator1.hasNext()){
        Object obj = iterator1.next();
        Map.Entry entry = (Map.Entry) obj;
        System.out.println(entry.getKey() + "---->" + entry.getValue());

    }
}

//定制排序
@Test
public void test2(){
    TreeMap map = new TreeMap(new Comparator() {
        @Override
        public int compare(Object o1, Object o2) {
            if(o1 instanceof User && o2 instanceof User){
                User u1 = (User)o1;
                User u2 = (User)o2;
                return Integer.compare(u1.getAge(),u2.getAge());
            }
            throw new RuntimeException("输入的类型不匹配！");
        }
    });
    User u1 = new User("Tom",23);
    User u2 = new User("Jerry",32);
    User u3 = new User("Jack",20);
    User u4 = new User("Rose",18);

    map.put(u1,98);
    map.put(u2,89);
    map.put(u3,76);
    map.put(u4,100);

    Set entrySet = map.entrySet();
    Iterator iterator1 = entrySet.iterator();
    while (iterator1.hasNext()){
        Object obj = iterator1.next();
        Map.Entry entry = (Map.Entry) obj;
        System.out.println(entry.getKey() + "---->" + entry.getValue());

    }
}

}