Java Map根据Key和value排序的代码

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;

import org.junit.Test;

public class MapSortTest {

	static Map<String, Integer> MAP = new HashMap<String, Integer>();

	static {
		MAP.put("ab", 27);
		MAP.put("aa", 25);
		MAP.put("c", 30);
		MAP.put("e", 21);
		MAP.put("d", 22);
	}

	@Test
	public void sortByKey() {
		TreeMap<String, Integer> treeMap = new TreeMap<String, Integer>(MAP);

		for (String key : treeMap.keySet()) {
			System.out.printf("key:%s, value:%d\n", key, MAP.get(key));
		}
	}

	@Test
	public void sortByValue() {
		ArrayList<Entry<String, Integer>> entries = new ArrayList<Entry<String, Integer>>(MAP.entrySet());
		Collections.sort(entries, new Comparator<Map.Entry<String, Integer>>() {
			public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
				return (o2.getValue() - o1.getValue()); // 降序
			}
		});

		for (Entry<String, Integer> entry : entries) {
			System.out.printf("key:%s, value:%d\n", entry.getKey(), entry.getValue());
		}
	}
}

 

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