Java集合类排序方式之一

package com.hyn;import java.util.ArrayList;import java.util.Collections;import java.util.HashMap;import java.util.List;import java.util.Map;public class DemoCollect {public static void main(String[] args) {Map<String, String> map = new HashMap<>();map.put("d", "d");map.put("k", "k");map.put("c", "c");map.put("a", "a");map.put("y", "y");List<String> keys = new ArrayList<String>(map.keySet());System.out.println(keys.toString());//[d, c, a, k, y]//集合类排序Collections.sort(keys);System.out.println(keys.toString());//[a, c, d, k, y]}}