对 List 里面 Map 的指定 key 进行排序

 

对 List 里面 Map 的指定 key 进行排序，重写Collections.sort() 方法

 new HashSet<>(list) 构造函数，会打乱 list 原有的顺序

 

package com.bugyun.tmp;


public class CollectionTool {
	
	/**
	 * @Description: 按照 args 由大到小排序
	 * @param list
	 * @param args  
	 * @return void  
	 * @throws
	 * @author beyond
	 * @date 2015-7-22
	 */
	public static void sort( List<Map<String, Object>> list , final String args ) {
		if(StringUtil.isNotEmpty(args)){
			Collections.sort(list, new Comparator<Map<String,Object>>() {
				public int compare(Map<String,Object> mapOne, Map<String,Object> mapTwo) {
					int flag = 0 ;
					Double  first = Double.valueOf(mapOne.get(args).toString());
					Double  second = Double.valueOf(mapTwo.get(args).toString());
					
					if((first - second) > 0){
						flag = -1 ;
					}else if((first - second) < 0){
						flag = 1 ;
					}else{
						flag = 0 ;
					}
					return flag ;
				};
			});
		}
	}
	
	/**
	 * @Description: 按照 args 由小到大排序
	 * @param list
	 * @param args  
	 * @return void  
	 * @author beyond
	 * @date 2015-8-12
	 */
	public static void sortRev( List<Map<String, Object>> list , final String args ) {
		if(StringUtil.isNotEmpty(args)){
			Collections.sort(list, new Comparator<Map<String,Object>>() {
				public int compare(Map<String,Object> mapOne, Map<String,Object> mapTwo) {
					int flag = 0 ;
					Double  first = Double.valueOf(mapOne.get(args).toString());
					Double  second = Double.valueOf(mapTwo.get(args).toString());
					
					if((first - second) > 0){
						flag = 1 ;
					}else if((first - second) < 0){
						flag = -1 ;
					}else{
						flag = 0 ;
					}
					return flag ;
				};
			});
		}
	}
	
	
	public static void main(String[] args) {
		List<Map<String,Object>> list = new ArrayList<Map<String,Object>>();  
        Map<String,Object> mapOne = new HashMap<String, Object>();  
        Map<String,Object> mapTwo = new HashMap<String, Object>();  
        Map<String,Object> mapThree = new HashMap<String, Object>();  
        Map<String,Object> mapFour = new HashMap<String, Object>();  
        Map<String,Object> mapFive = new HashMap<String, Object>();  
        Map<String,Object> mapSix = new HashMap<String, Object>();  
        Map<String,Object> map7 = new HashMap<String, Object>();  
        Map<String,Object> map8 = new HashMap<String, Object>();  
          
        mapOne.put("gradeId", "1");  
        mapOne.put("clzssId", "1");  
        mapOne.put("score", 0.0);  
          
        mapTwo.put("gradeId", "1");  
        mapTwo.put("clzssId", "2");  
        mapTwo.put("score", 0.8);  
          
        mapThree.put("gradeId", "1");  
        mapThree.put("clzssId", "3");  
        mapThree.put("score", 0.0);  
          
          
        mapFour.put("gradeId", "1");  
        mapFour.put("clzssId", "3");  
        mapFour.put("score", 1.0);  
          
        mapFive.put("gradeId", "1");  
        mapFive.put("clzssId", "2");  
        mapFive.put("score", 1.0);  
          
        mapSix.put("gradeId", "1");  
        mapSix.put("clzssId", "4");  
        mapSix.put("score", 0.0);  

        map7.put("gradeId", "1");  
        map7.put("clzssId", "4");  
        map7.put("score", 1.0);  

        map8.put("gradeId", "1");  
        map8.put("clzssId", "4");  
        map8.put("score", 0.8);  


        list.add(mapOne);  
        list.add(mapTwo);  
        list.add(mapThree);  
        list.add(mapFour);  
        list.add(mapFive);  
        list.add(mapSix); 
        list.add(map7);  
        list.add(map8); 
        
          
        sortRev(list,"score"); 
        
        /**
         * new HashSet<>(list) 构造函数，会打乱 list 原有的顺序
         */
        Set<Map<String,Object>> set = new HashSet<Map<String,Object>>(list);
        
        for(Map<String,Object> map : list){
        	System.err.println(map);
        }
        
        for(Map<String,Object> map : set){
        	System.out.println(map);
        }
	}
}