java获取字符串最长重复子串

    public static String maxSameStr(String str) {
        String nstr = "";
        if (str == null || str.length() == 0) return nstr;
        ArrayList list = new ArrayList<>();
        for (int i = 0; i < str.length(); i++) {
            for (int j = i + 1; j <= str.length(); j++) {
                String s = str.substring(i, j);
                if (list.contains(s)) {
                    if (s.length() > nstr.length()) nstr = s;
                }
                list.add(s);
            }
        }
        return nstr;
    }