Program that deletes one integer (or more if there's duplicates) from an array by it's value

Question

I need to write a program, which deletes a number of elements from an int array that are equal to some int value. Eventually I should get an array that isn't bigger than the initial one.

I mustn't use lists or any methods that do the deletion directly.

I tried to do this this way and I can't trace the flaw. I suppose, it should be in the last "for" construction but I'm not sure.


import java.util.Arrays;
import java.util.Scanner;

public class App {
public static void main(String\[\] args) {
Scanner scan = new Scanner(System.in);
System.out.print("Array size: ");
int sizeInput = scan.nextInt();

        int[] original = new int[sizeInput];
    
        System.out.print("Array itself: ");
        for (int i = 0; i < sizeInput; i++) {
            original[i] = scan.nextInt();
        }
    
        System.out.println("Number to be deleted: ");
        int dNumber = scan.nextInt();
    
        int[] newArr = new int[original.length];
    
        for (int i = 0; i < original.length - 1; i++) {
            int sum = 0;
            if (original[i] == dNumber) {
                newArr[i] = original[i + 1];
                sum = sum + 1;
            } else if (original[i] != dNumber) {
                newArr[i] = original[i + sum];
            } 
        }
        System.out.println(Arrays.toString(newArr));
    }

}

and here's what I got in my console eventually:

Array size: 5
Array itself: 1 2 3 4 5
Number to be deleted: 2
\[1, 3, 3, 4, 0\]

You see? In the output I get the second "3" for some reason and I also don't get why there's no last element of the initial array.

Please, explain what wrote wrong so that my code doesn't solve the problem. And please explain ho can I solve It. Thanks!

1. Right. That's what I expect. 2. The "sum" stands for, I'd say, the difference of indexes of the elements of the initial and new arrays — PDLIF, Dec 10 '22 at 18:34
Does this answer your question? [Remove duplicates from integer array](https://stackoverflow.com/questions/13912004/remove-duplicates-from-integer-array) — Aniruddh Parihar, Dec 10 '22 at 20:11
Another option is to do a two pass system. In the first pass, you just count the number of items to be deleted (or not deleted), so you know how big to make your new array. Then do a second pass and copy the items that won't be deleted to the new array. — Idle_Mind, Dec 10 '22 at 20:36
Being able to use a debugger will help you now and in the long run. A debugger allows you follow the code execution step-by-step, and watch how the variables change. — Old Dog Programmer, Dec 10 '22 at 20:38

score 0 · Accepted Answer · answered Dec 10 '22 at 18:30

You need a position int for the new array, so you go further only when you set a new value

int[] original = {1, 2, 3, 4, 5};
int dNumber = 2;

int[] newArr = new int[original.length];
int j = 0;
for (int val : original) {
    if (val != dNumber) {
        newArr[j] = val;
        j++;
    }
}
newArr = Arrays.copyOf(newArr, j); // truncate
System.out.println(Arrays.toString(newArr));
// [1, 3, 4, 5]

Program that deletes one integer (or more if there's duplicates) from an array by it's value

1 Answers1