核心类库-集合-TreeMap-两种添加方式的使用

import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.junit.Test;

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(u3,67);
		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() {
				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(u3,67);
			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());
			}
	}
}

---

public class User implements Comparable{
	private String name;
	private int age;
	@Override
	public String toString() {
		return "User [name=" + name + ", age=" + age + "]";
	}
	public User() {
		super();
	}
	public User(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + age;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		System.out.println("User equals()..");
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		User other = (User) obj;
		if (age != other.age)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}
	
	//按照姓名从大到小排列，年龄从小到大排列
	@Override
	public int compareTo(Object o) {
		if(o instanceof User) {
			User user=(User)o;
//			return this.name.compareTo(user.name);
//			return -this.name.compareTo(user.name); //从大到小
			int compare = -this.name.compareTo(user.name);
			if(compare != 0) {
				return compare;
			}else {
				return Integer.compare(this.age, user.age);
			}
		}else {
			throw new RuntimeException("输入的类型不匹配");
		}
	}
	
}