Java实现myToString

    public static String myToString(int[] arr) {
        if (arr == null) {
            return null;
        }
        if (arr.length == 0) {
            return "";
        }
        int i = 0;
        String str = "[";
        for (i = 0; i < arr.length-1; i++) {
            str += arr[i];
            str += ",";
        }
        if (i == arr.length-1) {
            str += arr[i];
        }
        str += "]";
        return str;
    }

    public static void main(String[] args) {
        int[] arr = {1,2,3,7,8,9};
        System.out.println(myToString(arr));
    }

输出结果：