TreeMapTest

package maptest;

import listtest.Person;
import org.junit.Test;

import java.util.*;

/**
 *
 *
 *
 * @author FuJingchao
 * @Date: 2021/12/25 - 13:18
 */
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
    @Test
    public void test1(){
        TreeMap map = new TreeMap();
        Person p1 = new Person("Tom",23);
        Person p2 = new Person("jack",32);
        Person p3 = new Person("Bob",18);
        Person p4 = new Person("Jam",15);
        map.put(p1,98);
        map.put(p2,89);
        map.put(p3,96);
        map.put(p4,100);

        Set entrySet = map.entrySet();//entrySet集合中的元素都是entry
        Iterator iterator = entrySet.iterator();
        while (iterator.hasNext()){
            Object obj = iterator.next();
            Map.Entry entry = (Map.Entry) obj;
            System.out.println(entry.getKey()+"--->"+entry.getValue());
        }
    }

    //定制排序:按照姓名从小到大排序,再按照年龄从小到大排序
    @Test
    public void test2(){
        TreeMap map = new TreeMap(new Comparator() {
            @Override
            public int compare(Object o1, Object o2) {
                if(o1 instanceof Person && o2 instanceof Person){
                    Person p1 = (Person) o1;
                    Person p2 = (Person) o2;
                    int compare = p1.getName().compareTo(p2.getName());
                    if(compare != 0){
                        return compare;
                    }else {
                        return Integer.compare(p1.getAge(),p2.getAge());
                    }
                }
                throw new RuntimeException("类型输出不一致");
            }
        });
        Person p1 = new Person("Tom",23);
        Person p2 = new Person("Jack",32);
        Person p3 = new Person("Bob",18);
        Person p4 = new Person("Jam",15);
        map.put(p1,98);
        map.put(p2,89);
        map.put(p3,96);
        map.put(p4,100);

        Set entrySet = map.entrySet();//entrySet集合中的元素都是entry
        Iterator iterator = entrySet.iterator();
        while (iterator.hasNext()){
            Object obj = iterator.next();
            Map.Entry entry = (Map.Entry) obj;
            System.out.println(entry.getKey()+"--->"+entry.getValue());
        }
    }


}