How to split an Integer into an Array using Java?

问题

I apologise if this has already been asked before, but I was unable to find a conclusive answer after some extensive searching, so I thought I would ask here. I am a beginner to Java (to coding, in general) and was tasked with writing a program that takes a user-inputted 3 digit number, and adds those three digits.

Note: I cannot use loops for this task, and the three digits must all be inputted at once.

String myInput;
    myInput =        
    JOptionPane.showInputDialog(null,"Hello, and welcome to the ThreeDigit program. "
    + "\nPlease input a three digit number below. \nThreeDigit will add those three numbers and     display their sum.");
    int threedigitinput;
    threedigitinput = Integer.parseInt(myInput);

回答1:

There are a number of ways, one of which would be...

    String ss[] = "123".split("");
    int i = 
            Integer.parseInt(ss[0]) + 
            Integer.parseInt(ss[1]) + 
            Integer.parseInt(ss[2]);
    System.out.println(i);

another would be...

    String s = "123";
    int i = 
            Character.getNumericValue(s.charAt(0)) +
            Character.getNumericValue(s.charAt(1)) +
            Character.getNumericValue(s.charAt(2));
    System.out.println(i);

and still another would be...

    String s = "123";
    int i = 
            s.charAt(0) +
            s.charAt(1) +
            s.charAt(2) - 
            (3 * 48);
    System.out.println(i);

BUT hard coding for 3 numbers isn't very useful beyond this simple case. So how about recursion??

public static int addDigis(String s) {
        if(s.length() == 1)
            return s.charAt(0) - 48;
        return s.charAt(0) - 48 + addDigis(s.substring(1, s.length()));
}

Output for each example: 6

回答2:

you can use integer math to come up with the three numbers seperately

int first = threedigitinput / 100;
int second = (threedigitinput % 100) / 10;
int third = threedigitinput % 10;

回答3:

If I understand your question, you could use Character.digit(char,int) to get the value for each character with something like -

int value = Character.digit(myInput.charAt(0), 10)
        + Character.digit(myInput.charAt(1), 10)
        + Character.digit(myInput.charAt(2), 10);

回答4:

Classic example of using divmod:

public class SumIntegerDigits {
    public static void main(String[] args) {
        System.out.println(sumOfDigitsSimple(248));    // 14
        System.out.println(sumOfDigitsIterative(248)); // 14
        System.out.println(sumOfDigitsRecursive(248)); // 14
    }

    // Simple, non-loop solution
    public static final int sumOfDigitsSimple(int x) {
        int y = x % 1000; // Make sure that the value has no more than 3 digits.
        return divmod(y,100)[0]+divmod(divmod(y,100)[1],10)[0]+divmod(y,10)[1];
    }

    // Iterative Solution
    public static final int sumOfDigitsIterative(int x) {
        int sum = 0;
        while (x > 0) {
            int[] y = divmod(x, 10);
            sum += y[1];
            x = y[0];
        }
        return sum;
    }

    // Tail-recursive Solution
    public static final int sumOfDigitsRecursive(int x) {
        if (x <= 0) {
            return 0;
        }
        int[] y = divmod(x, 10);
        return sumOfDigitsRecursive(y[0]) + y[1];
    }

    public static final int[] divmod(final int x, int m) {
        return new int[] { (x / m), (x % m) };
    }
}

来源：https://stackoverflow.com/questions/26319579/how-to-split-an-integer-into-an-array-using-java

标签

java

arrays

integer