lambda表达式之集合排序工具类

淩亂°似流年 2023-06-06 03:44 24阅读 0赞

使用java8的函数式接口简化集合排序中Compartor的写法

/**
     * 集合排序工具类
     * 函数式接口简化代码
     */
    public class CollectionSort {
        public static void main(String[] args) {
            Map<String,Integer> dataMap = new HashMap<>();
            dataMap.put("c",2);
            dataMap.put("a",7);
            dataMap.put("f",5);
            dataMap.put("p",9);
            dataMap.put("z",8);
            Map newMap = sortValue(dataMap);
            System.out.println(newMap);
        }
        public static <T extends Comparable> Map sortKey(Map<String,T> dataMap){
            List<Map.Entry<String,T>> entryList = new ArrayList<>(dataMap.entrySet());
            Collections.sort(entryList,(m1,m2)->m1.getKey().compareTo(m2.getKey()));
            return SortList(entryList);
        }
    
        public static <T extends Comparable> Map sortKeyDesc(Map<String,T> dataMap){
            List<Map.Entry<String,T>> entryList = new ArrayList<>(dataMap.entrySet());
            Collections.sort(entryList,(m1,m2)->m2.getKey().compareTo(m1.getKey()));
            return SortList(entryList);
        }
    
        public static <T extends Comparable> Map sortValue(Map<String,T> dataMap){
            List<Map.Entry<String,T>> entryList = new ArrayList<>(dataMap.entrySet());
            Collections.sort(entryList,(m1,m2)->m1.getValue().compareTo(m2.getValue()));
            return SortList(entryList);
        }
    
        public static <T extends Comparable> Map sortValueDesc(Map<String,T> dataMap){
            List<Map.Entry<String,T>> entryList = new ArrayList<>(dataMap.entrySet());
            Collections.sort(entryList,(m1,m2)->m2.getValue().compareTo(m1.getValue()));
            return SortList(entryList);
        }
    
        private static <T extends Comparable> Map SortList(List<Map.Entry<String,T>> entryList) {
            Iterator<Map.Entry<String,T>> it = entryList.iterator();
            Map<String,T> tempMap = new LinkedHashMap<>();
            while(it.hasNext()){
                Map.Entry<String,T> mapEntry = it.next();
                tempMap.put(mapEntry.getKey(),mapEntry.getValue());
            }
            return tempMap;
        }
    }