比较两个集合是否有重复的值

 /**
     * 比较两个集合是否有重复的值
     * */
    //一般法
    public static boolean isRepeat(List<Object> list1, List<Object> list2) {
        for (Object o1 : list1) {
            for (Object o2 : list2) {
                if (o1.equals(o2))
                    return true;
            }
        }
        return false;
    }
    //最优法
    public static boolean isRepeat2(List<Object> list1, List<Object> list2) {
        Set<Object> set1 = new HashSet<Object>(list1.size());
        set1.addAll(list1);
        Set<Object> set2 = new HashSet<Object>(list2.size());
        set2.addAll(list2);
        Set<Object> setAll = new HashSet<Object>(list1.size() + list2.size());
        setAll.addAll(set1);
        setAll.addAll(set2);
        int setSize = set1.size() + set2.size();
        if (setSize != setAll.size()) {
            return true;
        }
        return false;
    }