兩個list查看是否有交集

String s1 = "50000,100000,200000,300000,500000,";
        String s2 = "10000,30000,50000,100000,";
        String[] a1 = s1.split(",");
        String[] a2 = s2.split(",");
        List<String> list = new ArrayList(Arrays.asList(a1));
        list.retainAll(Arrays.asList(a2)); // list 中的就是交集了
        for(String s : list){
            System.out.println(s);
        }

如果僅僅需要知道是否有交集

Collections.disjoint(list1,list2)

false: 有交集 
true: 沒有交集