map自定义排序，根据键或者值排队

╰+哭是因爲堅強的太久メ 2022-04-04 11:00 383阅读 0赞

核心比较器  
比较器之根据键排序

package cn.com.hongyitech.accountsystem.utils;
    
    import java.util.Comparator;
    
    class MapKeyComparator implements Comparator<String>{
    
        @Override
        public int compare(String key1, String key2) {
            
            return key1.compareTo(key2);
        }
    }

比较器之根据值排序

package cn.com.hongyitech.accountsystem.utils;
    
    import java.util.Comparator;
    import java.util.Map;
    import java.util.Map.Entry;
    
    class MapValueComparator implements Comparator<Map.Entry<String, String>> {
    
    	@Override
    	public int compare(Entry<String, String> map1, Entry<String, String> map2) {
    
    		return map1.getValue().compareTo(map2.getValue());
    	}
    }

根据键排序

/**
    	 * 使用 Map按key进行排序
    	 * 
    	 * @param map
    	 * @return
    	 */
    	public static Map<String, String> sortMapByKey(Map<String, String> map) {
    		if (map == null || map.isEmpty()) {
    			return null;
    		}
    
    		Map<String, String> sortMap = new TreeMap<String, String>(new MapKeyComparator());
    
    		sortMap.putAll(map);
    
    		return sortMap;
    	}

根据值排序

/**
    	 * 使用 Map按value进行排序
    	 * 
    	 * @param map
    	 * @return
    	 */
    	public static Map<String, String> sortMapByValue(Map<String, String> oriMap) {
    		if (oriMap == null || oriMap.isEmpty()) {
    			return null;
    		}
    		Map<String, String> sortedMap = new LinkedHashMap<String, String>();
    		List<Map.Entry<String, String>> entryList = new ArrayList<Map.Entry<String, String>>(oriMap.entrySet());
    		Collections.sort(entryList, new MapValueComparator());
    
    		Iterator<Map.Entry<String, String>> iter = entryList.iterator();
    		Map.Entry<String, String> tmpEntry = null;
    		while (iter.hasNext()) {
    			tmpEntry = iter.next();
    			sortedMap.put(tmpEntry.getKey(), tmpEntry.getValue());
    		}
    		return sortedMap;
    	}

测试用例

public static void main(String[] args) {
    
    		Map<String, String> map = new TreeMap<String, String>();
    
    		map.put("2018-12-06", "1");
    		map.put("2018-12-03", "2");
    		map.put("2018-12-07", "4");
    		map.put("2018-12-04", "2");
    		map.put("2018-12-01", "3");
    
    		Map<String, String> resultMapByKey = sortMapByKey(map); // 按Key进行排序
    		Map<String, String> resultMapByValue = sortMapByValue(map); // 按Value进行排序
    
    		for (Map.Entry<String, String> entry : resultMapByKey.entrySet()) {
    			System.out.println(entry.getKey() + " " + entry.getValue());
    		}
    		System.out.println("******上面根据key*********************下面根据value********");
    		for (Map.Entry<String, String> entry : resultMapByValue.entrySet()) {
    			System.out.println(entry.getKey() + " " + entry.getValue());
    		}
    	}

结果

2018-12-01 3
    2018-12-03 2
    2018-12-04 2
    2018-12-06 1
    2018-12-07 4
    ******上面根据key*********************下面根据value********
    2018-12-06 1
    2018-12-03 2
    2018-12-04 2
    2018-12-01 3
    2018-12-07 4