需要将 arrays 相乘的代码，如果数组为空则返回 0

Question

I need code that multiplies array contents which are formed by test

public void testMulArray() {
    FirstSteps firstSteps = new FirstSteps();
    int[] array1 = {1, 2, 3};
    assertEquals(6, firstSteps.mul(array1));
    int[] array2 = {-1, -2, 3};
    assertEquals(6, firstSteps.mul(array2));
    int[] array3 = {1, 2, 0};
    assertEquals(0, firstSteps.mul(array3));
    int[] array4 = {};
    assertEquals(0, firstSteps.mul(array4));
}

Before this, I made a similar code that returns the sum of array contents that is formed by the test

public void testSumArray() {
    FirstSteps firstSteps = new FirstSteps();
    int[] array1 = {1, 2, 3};
    assertEquals(6, firstSteps.sum(array1));
    int[] array2 = {-1, -2, 3};
    assertEquals(0, firstSteps.sum(array2));
    int[] array3 = {};
    assertEquals(0, firstSteps.sum(array3));
}

Code for sum is

public class FirstSteps {
    public int sum(int[] array){
        int sum = 0;
        for (int value : array) {
            sum += value;
        }
        return sum;
    }
}

It worked and for multiplying I made similar code

public class FirstSteps {
    public int mul(int[] array){
        int mul = 0;
        for (int value : array) {
            mul *= value;
        }
        return mul;
    }
}

Answer 1

You make mul = 0 , but, zero multiplies by any number results zero!

Instead you should make that initial value mul = 1 .

public class FirstSteps {
    public int mul(int[] array){
        if (array.length == 0) return 0;
        int mul = 1; 
        for (int value : array) {
            mul *= value;
        }
        return mul;
    }
}