Returning the last digit of every number in an array

Question

My problem is that I'm trying to return the last digit of every element in an int array but the function below rather returns the last element of the array. How would I go about doing this.

Array: {10, 12, 41, 23, 71}

Expected output: 0, 2, 1, 3, 1

public class TestForEachLoop
{
    private int[] iLoop = new int[5];
    
    public int getLastDigit(){

        int[] iLoop = new int[]{10, 12, 41, 23, 71};
        int lastnumber = iLoop[iLoop.length - 1];
        return lastnumber;
    }    
}

score 2 · Answer 1 · edited Nov 22 '20 at 19:20

2

You need to use a for loop to iterate over the array.

for (int i = 0; i < array.length; i++ ) {
   // do something with array[i]
}

To get the last digit of each number, you should use the remainder % operator. For two numbers m and n, m % n returns the remainder of m divided by n. Beware of the negative numbers you might need to use Math.abs() as well.

edited Nov 22 '20 at 19:20

dreamcrash

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answered Nov 22 '20 at 18:44

WJS

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So much for trying to help someone without giving them the solution. – WJS Nov 22 '20 at 19:09

ABC · Accepted Answer · 2020-11-22T19:14:27.067

1

You can use modulo operator to get the last digit of a number and then use the abs method in the Math class to get the positive value.

public class Main {
    
    public static int getLastDigit(int n){
        int lastDigit = Math.abs(n % 10);
        return lastDigit;
    }
    
    public static void main(String[] args){
        int[] iLoop = new int[]{10, 12, 41, 23, 71};
        for(int i = 0; i < iLoop.length; i++){
            System.out.print(getLastDigit(iLoop[i]) + " ");
        }
    }
}

edited Nov 22 '20 at 19:14

answered Nov 22 '20 at 18:50

ABC

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Hi, do you mind updating you answer to cover negative numbers? otherwise your current code will fail – dreamcrash Nov 22 '20 at 19:04

dreamcrash · Answer 3 · 2020-11-22T19:54:53.187

You can retrieve the last digit of a number by using the modulus '%' operation (more about it here) combined with Math.abs() to avoid getting into problems with negative numbers. Then you just need to apply that logic to each element of your array.

You can do it with streams from Java 8 very nicely:

  int[] iLoop = new int[]{10, 12, 41, 23, 71};
  Arrays.stream(iLoop).forEach(n -> System.out.print(Math.abs(n) % 10 + " "));

with a running example:

import java.util.Arrays;
class Main {  
  public static void main(String args[]) { 
      
      int[] iLoop = new int[]{10, 12, 41, 23, 71};
      Arrays.stream(iLoop).forEach(n -> System.out.print(Math.abs(n) % 10 + " "));
  } 
}

score -1 · Answer 4 · edited Nov 23 '20 at 04:08

public int getLastDigit(int number){
    String sNumber=Integer.toString(number);
    return Integer.parseInt(String.valueOf(sNumber.charAt(sNumber.length() - 1))); //parseInt only accept String value
}

public int[] getVectorLastNumbers(int[] numbers){
    int[] lastNumbers=new int[numbers.length];
    for(int i=0;i<numbers.length;i++){
     lastNumbers[i]=getLastDigit(numbers[i]);  
    }
   return lastNumbers;
}

Returning the last digit of every number in an array

4 Answers4