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Java program to remove duplicate elements from an array

In this java program, we are going to read an array and removing the duplicate elements from it. By Preeti Jain Last updated : December 23, 2023

Problem statement

Given an array of integers and we have to remove duplicate elements using java program.

Example

Input array elements:
1, 2, 3, 1, 2, 3, 4

Output:
Elements after removing duplicates
1, 2, 3, 4

Program to remove duplicate elements in java

import java.util.Scanner;

public class RemoveDuplicateElementFromArray {
  public static void main(String[] args) {
    /* Array instantiation */
    int[] arr_elements = new int[20];

    /* initial_element variable initialize by 0 and 
    point to the first element of the array */
    /* next_element points to next element of array */
    int initial_element, next_element;
    int i;

    /*Create Scanner Object */
    Scanner sc = new Scanner(System.in);

    /*Display array size for user*/
    System.out.print("Enter array size: ");
    int arr_size = sc.nextInt();

    /*Display message for array element*/
    System.out.println("Read Array Elements From User :");

    /*Loop to take input array elements*/
    for (i = 0; i < arr_size; ++i) {
      System.out.print("Enter array elements of index " + i + ": ");
      arr_elements[i] = sc.nextInt();
    }

    /* Display array before removing duplicate element */
    System.out.println("Before removing duplicate element array are :");

    /* Loop for displaying array elements */
    for (i = 0; i < arr_size; ++i) {
      System.out.println(arr_elements[i]);
    }

    /* Get new line
    System.out.println();
    /* Display array after removing duplicate array element */
    System.out.println("After removing duplicate element array are :");
    for (initial_element = 0; initial_element < arr_size; ++initial_element) {
      for (next_element = initial_element + 1; next_element < arr_size;) {
        /* if initial_element matches to next_element 
        then take next _element and matches till end */
        if (arr_elements[initial_element] == arr_elements[next_element]) {
          for (int temp = next_element; temp < arr_size; ++temp) {
            arr_elements[temp] = arr_elements[temp + 1];
          }
          arr_size = arr_size - 1;
        } else
          next_element++;
      }
    }

    /* Loop to display array after removing duplicate element */
    for (i = 0; i < arr_size; ++i)
      System.out.println(arr_elements[i]);
  }
}

Output

Enter array size: 7

Read Array Elements From User :
Enter array elements of index 0: 1
Enter array elements of index 1: 2
Enter array elements of index 2: 3
Enter array elements of index 3: 1
Enter array elements of index 4: 2
Enter array elements of index 5: 3
Enter array elements of index 6: 4

Before removing duplicate element array are :
1
2
3
1
2
3
4

After removing duplicate element array are :
1
2
3
4

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