在线急等！求一算法！

Question

List l = new ArrayList();
l.add("a");
l.add("a");
l.add("b");
l.add("a");
l.add("c");
l.add("d");
l.add("a");
有这么一个list ，我想得到的结果是lista="a,a,a,a",listb="b",listc="c",listd="d",请问该如何做呢？

Answer 1

public static void main(String[] arsgs) {
List l = new ArrayList();
l.add("b");
l.add("a");
l.add("a");
l.add("a");
l.add("c");
l.add("d");
l.add("a");

        Map<String,String> demo = mySplit(l);
        for (Map.Entry<String,String> entry : demo.entrySet()) {
            System.out.println("key=" + entry.getKey());
            System.out.println("value=" + entry.getValue());
        }
    }


    public static Map<String, String> mySplit(List<String> list) {
            Map<String, String>  result = new TreeMap<String, String>();
            if(list == null ) return null;
            Collections.sort(list);
            for(int index = 0, len= list.size(); index <len; index++) {
                String currentElement = list.get(index);
                if(currentElement == null) {
                    continue;
                }
                else {
                    String key = "list"  + currentElement;
                    result.put(key, result.containsKey(key) ?  result.get( key) + "," + currentElement : currentElement);
                }
            }

            return result;
    }