Error when setting entry of int[] array to null

Question

I had the following idea to take an array and remove any duplicates. However, I am getting the error "error: incompatible types: cannot be converted to int" referring to the part of the code where I set temp[i] = null. Is it possible to do this? How can I fix this problem?

public static int[] withoutDuplicates(int[] x) {
    int[] temp = new int[x.length];
    int count = 0;
    for (int i = x.length - 1; i >= 0; i--) {
      for (int j = i-1; j >= 0; j--) {
        if (temp[i] == x[j]) {
          temp[i] = null;
          count++;
        }
      }
    }
    int size = x.length - count;
    int[] a = new int[size];
    int pos = 0;
    for (int i = 0; i < x.length; i++) {
      if (temp[i] != null) {
        a[pos] = temp[i];
        pos++;
      }
    }
    return a;
  }

null is a reference, while int is a primitive type. You cannot assign a reference to a primitive. Use Integer instead of int — fps
– fps, Commented Oct 9, 2020 at 20:06

Nowhere Man · Accepted Answer · 2020-10-09 20:50:52Z

Stream-based solution is concise but for your task/requirements you could be using just a temporary boolean array to mark positions of duplicates:

public static int[] withoutDuplicates(int[] x) {
    boolean[] duplicated = new boolean[x.length];
    int count = 0;
    for (int i = x.length - 1; i > 0; i--) {
        for (int j = i-1; j >= 0; j--) {
            if (x[i] == x[j]) {
                duplicated[i] = true;
                count++;
             }
        }
    }
    int size = x.length - count;
    int[] a = new int[size];
    for (int i = 0, pos = 0; pos < size && i < x.length; i++) {
        if (!duplicated[i]) {
            a[pos++] = x[i];
        }
    }
    return a;
}

Test:

int[] arr1 = {1, 2, 3, 4, 3, 5, 2};
int[] arr2 = {1, 2, 3, 4, 0, 5, 6};
        
System.out.println(Arrays.toString(withoutDuplicates(arr1)));
System.out.println(Arrays.toString(withoutDuplicates(arr2)));

output

[1, 2, 3, 4, 5]
[1, 2, 3, 4, 0, 5, 6]

David SN · Accepted Answer · 2020-10-09 20:58:04Z

1

You can't assign a null to a primitive type int but you can assign a null to the wrapper object Integer.

To remove the duplicates of an int array you could use something like this:

myIntArray = Arrays.stream(myIntArray).distinct().toArray();

edited Oct 9, 2020 at 20:58

answered Oct 9, 2020 at 20:12

David SN

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MC Emperor Over a year ago

Java 14 needed? Java ≥ 8 is sufficient.

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