查找两个数字之间的相似整数

Question

There are two number variables. I want to confirm and print similar integers between these two numbers. Eg. Int num1 = 6229; int num2 = 2394. I want the program to print the shared integers of '2' and '9' and return 'true' for confirmation.

public class Main {

    public static void main(String[] args) {
        System.out.println(hasSharedDigit(6229, 2394));
    }

    public static boolean hasSharedDigit(int firstNumber, int secondNumber) {

        int firstDigit;
        int secondDigit;

        while ((firstNumber > 0) && (firstNumber < 10000)) {
            firstDigit = firstNumber % 10;
            firstNumber /= 10;
            while ((secondNumber > 0) && (secondNumber < 10000)) {
                secondDigit = secondNumber % 10;
                secondNumber /= 10;
                if (!(firstDigit == secondDigit)) {
                    continue;
                }
                System.out.println(secondDigit);
                return true;
            }
        }
        return false;
    }
}

Answer 1

The DRY principle (Don't Repeat Yourself) guides you to move repeated code to a reusable helper method, so you should create a method that extracts the digits of a number into a Set , allowing you to easily use set intersection to find the digits they have in common.

For this, aBitSet is the most appropriate "Set", so you could write the helper method like this:

private static BitSet digitsOf(int number) {
    BitSet digits = new BitSet(10);
    do {
        digits.set(number % 10);
    } while ((number /= 10) != 0);
    return digits;
}

Now it's very easy to find shard digits of two numbers:

public static boolean hasSharedDigit(int firstNumber, int secondNumber) {
    BitSet digits = digitsOf(firstNumber);
    digits.and(digitsOf(secondNumber));
    System.out.println(digits);
    return ! digits.isEmpty();
}

Test

System.out.println(hasSharedDigit(6229, 2394));
System.out.println(hasSharedDigit(0, 123));
System.out.println(hasSharedDigit(0, 404));

Output

{2, 9}
true
{}
false
{0}
true