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
