博客

如题，获取一个数组中两两组合

示例:给定一个List<1,2,3,4>

输出:1,2 1,3 1,4 2,3 2,4 3,4

demo:

 public static void main(String[] args) {
        List<Pair<String, String>> pairs = combineTwoElement(Lists.newArrayList("1", "2","3","4"));
        List<Pair<String, String>> pairs1 = combineTwoElement(Lists.newArrayList("1", "2","3","4","5"));
        System.out.println(pairs);
        System.out.println(pairs1);

    }

    public static List<Pair<String, String>> combineTwoElement(List<String> list) {
        List<Pair<String, String>> resultList = Lists.newArrayListWithExpectedSize(list.size()*list.size()/2);
        if (CollectionUtils.isEmpty(list)) {
            return null;
        }
        if (list.size() >= 2) {
            for (int j = 0; j < list.size(); j++) {
                resultList.addAll(ll(list.subList(j,list.size())));
            }

        }
        return resultList;
    }


    public static List<Pair<String, String>> ll (List<String> list){
        List<Pair<String, String>> resultList = Lists.newArrayListWithExpectedSize(list.size()*list.size()/2);

        for (int j = 1; j < list.size(); j++) {
            resultList.add(new Pair<>(list.get(0), list.get(j)));
        }
        return  resultList;
    }

结果: