从数组列表中打印负数的位置

Question

I have been looking over and over this code and can't seem to figure out the answer. However, I know it is a simple solution, I just can't find it as of right now...

Basicly, what i'm trying to is find the postion to all the negative numbers from the array-list. (Positionorder: 0,1,2,3,4,5,6,7,8) Then print which position the negative numbers have. When compiling the code Java tells me what the error is:

Test.java:11: error: bad operand types for binary operator '<='

 while (a<=0) { ^ 

first type: int[]
second type: int
1 error"**

But how can I resolve the problem, anyone who can guide me in the right direction and also an explanation of why while (a < 0) is not allowed in the current code. (The task is to do this with while )

String posNegative = 0;
int[] a = {1, 4, 5, -2, -4, 6, 10, 3, -2};
while (a < 0) {
    posNegative++;
    System.out.println(posNegative);
}

Answer 1

There are several problems with your code. First of all, what you actually want for your problem is as simple as this:

int[] a = {1, 4, 5, -2, -4, 6, 10, 3, -2};
for (int i = 0; i < a.length; i++) {
    if (a[i] < 0) {
        System.out.println(i);
    }
}

Now let's look at your code. If you look at the error message it says that you are trying to compare an int[] , a, and an int , 0. An int[] is a completely different type than int , so they cannot be compared. Read int[] as "int-array".

There's also the issue of this line:

String posNegative = 0;

I'm guessing that what you are thinking is that you need posNegative to be a String so that you can print it. That, however, is not necessary. System.out.println() can take pretty much anything you throw at it. When you declare a number, declare it as

int posNegative = 0;

Answer 2

a is an array. An array cannot be less than zero.

You can iterate through the array either by putting

for (int item : a) {
    ...

or

for (int i = 0; i < a.length; ++i) {
    item = a[i];
    ....
}

Answer 3

You are confusing the array with its contents. The array itself cannot be a negative integer, because it's an array, not an integer. To access the array's contents use a[n] where n is the index of the element you want to access.

int[] a = {1, 4, 5, -2, -4, 6, 10, 3, -2};
for (int n = 0; n < a.length; n++) {
    if (a[n] < 0) {
        System.out.println(n);
    }
}

Answer 4

a is not an int, it is an array of ints. If your intent is to loop over an array, you can use an enhanced for loop:

for(int i : a)
{
    posNegative++;
    if(i < 0)
    {
        System.out.println(posNegative);
    }
}