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]
				
	}
}