Java：命令行输入的总和给出了array * answer的长度

Question

I am inputing five or more variables on the command line and creating an array out of them. I'm then adding the values of these but I'm not sure why it's not working.

My code is:

public static void main(String args[]) {
    int t = args.length;
    int[] u;
    u = new int[t];
    int v = 0;
    for (int i=0; i<t; i++) {
        u[i]= Integer.parseInt(args[i]);
        for (int j=0; j<t; j++) {
            v = v + u[i];
            System.out.println(v);
        }
    }
}

However if I input 5 ones this outputs 25.

I'm not sure where I have gone wrong and any help would be greatly appreciated.

NOTE: My task requires I use no library functions.

Answer 1

1) You have a for loop inside another for loop that is causing the trouble.

2) Also watch out for your variable naming --> use variable names that express/describe their purpose. The variable name t is not too descriptive.

3) Also there is no need to create extra variables / arrays. Just loop through the input and add them to the sum.

public static void main(String args[]) {
  int sum = 0;
  for (int i=0; i<args.length; i++) {
    sum  += Integer.parseInt(args[i]);
  }
  System.out.println(sum);
}

---

4) Thanks to Java 8 you can do a (bit complex) one liner:

public static void main(String args[]) {
    System.out.println(Arrays.stream(myarray).mapToInt(Integer::parseInt).sum());
}

• Create a Stream of Strings ( Arrays.stream(args) )
• Convert these to IntStream ( mapToInt(Integer::parseInt) )
• Get the Sum of the IntegerStream via sum()

Answer 2

Your inner for loop makes no sense and seems to be the cause of your problem. Effectively you are doing t * t loops, which in your case is 5 * 5 which is why you get a result of 25 based on input of all 1's.

You only need to loop over the input array a single time, like this:

public static void main(String args[]) {
    int t = args.length;
    int[] u;
    u = new int[t];
    int v = 0;

    for (int i=0; i<t; i++) {
        u[i]= Integer.parseInt(args[i]);
        v = v + u[i];
    }

    System.out.println(v);
}

---

On a side note there is no reason to actually store an int array unless you are planning on using it later for something else. Based on this specific requirement, it would be better written like so:

public static void main(String args[]) {
    int length = args.length;
    int total = 0;

    for (int i = 0; i < length; i++) {
        int number = Integer.parseInt(args[i]);
        total += number;
    }

    System.out.println(total);
}