Map双列集合 - TreeMap
package com.atguigu.java;import org.junit.Test;import java.util.*;/** * @author shkstart * @create 2019 下午 3:46 */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()); } }}
