//定义一个100元素的集合，包含A-Z
List<String> list = new LinkedList<>();
for (int i =0;i<100;i++){
    list.add(String.valueOf((char)('A'+Math.random()*('Z'-'A'+1))));
}
System.out.println(list);
//统计集合重复元素出现次数，并且去重返回hashmap
Map<String, Long> map = list.stream().
    collect(Collectors.groupingBy(Function.identity(),Collectors.counting()));
System.out.println(map);
//由于hashmap无序，所以在排序放入LinkedHashMap里(key升序)
Map<String, Long> sortMap = new LinkedHashMap<>();
map.entrySet().stream().sorted(Map.Entry.comparingByKey()).
    forEachOrdered(e -> sortMap.put(e.getKey(), e.getValue()));
System.out.println(sortMap);
//获取排序后map的key集合
List<String> keys = new LinkedList<>();
sortMap.entrySet().stream().forEachOrdered(e -> keys.add(e.getKey()));
System.out.println(keys);
//获取排序后map的value集合
List<Long> values = new LinkedList<>();
sortMap.entrySet().stream().forEachOrdered(e -> values.add(e.getValue()));
System.out.println(values);