Java Program to Count Array Duplicates

Write a Java Program to Count Array Duplicates with an example or how to write a program to find and count the duplicates in a given array.

In this Java count duplicate array number example, we used a while loop to iterate Dup_Count_arrr array, count duplicate items (item shown more than once), and print the total.

package ArrayPrograms;

public class CountArrayDuplicates {
	
	public static void main(String[] args) {
		
		int i = 0, j, dup_count = 0;
		int[] Dup_Count_arr = {10, 15, 25, 10, 8, 12, 10, 15, 55, 10, 60};
		
		while(i < Dup_Count_arr.length) 
		{
			j = i + 1;
			while(j < Dup_Count_arr.length)
			{		
				if(Dup_Count_arr[i] == Dup_Count_arr[j]) {
					dup_count++;
					break;
				}
				j++;
			}
			i++;
		}
		System.out.println("\nThe Total Number of Duplicates  = " + dup_count);
	}
}

The Total Number of Duplicates  = 4

Java Program to Count Duplicates in an Array using For Loop

package ArrayPrograms;

import java.util.Scanner;

public class CountArrayDuplicates1 {
	private static Scanner sc;
	
	public static void main(String[] args) {
		int Size, i, j, dup_count = 0;
		
		sc = new Scanner(System.in);
		
		System.out.print("\nPlease Enter the Duplicate Array size  : ");
		Size = sc.nextInt();
		
		int[] Dup_Count_arr = new int[Size];
		
		System.out.format("\nEnter Duplicate Array %d elements : ", Size);
		for(i = 0; i < Size; i++) 
		{
			Dup_Count_arr[i] = sc.nextInt();
		}
		
		for(i = 0; i < Size; i++) 
		{
			for(j = i + 1; j < Size; j++)
			{
				if(Dup_Count_arr[i] == Dup_Count_arr[j]) {
					dup_count++;
					break;
				}
			}
		}
		System.out.println("\nThe Total Number of Duplicates  = " + dup_count);
	}
}

In this count duplicate array items in example, we created a separate function CountDuplicateElement to count and return duplicate count.

package ArrayPrograms;

import java.util.Scanner;

public class CountArrayDuplicates2 {
	private static Scanner sc;
	
	public static void main(String[] args) {
		int Size, i;
		
		sc = new Scanner(System.in);
		
		System.out.print("\nPlease Enter the Duplicate Array size  : ");
		Size = sc.nextInt();
		
		int[] Dup_Count_arr = new int[Size];
		
		System.out.format("\nEnter Duplicate Array %d elements : ", Size);
		for(i = 0; i < Size; i++) 
		{
			Dup_Count_arr[i] = sc.nextInt();
		}
		
		int dup_count = CountDuplicateElement(Dup_Count_arr, Size);
		
		System.out.println("\nThe Total Number of Duplicates  = " + dup_count);
	}
	
	public static int CountDuplicateElement(int[] Dup_Count_arr, int Size ) {
		int i, j, dup_count = 0;
		
		for(i = 0; i < Size; i++) 
		{
			for(j = i + 1; j < Size; j++)
			{
				if(Dup_Count_arr[i] == Dup_Count_arr[j]) {
					dup_count++;
					break;
				}
			}
		}
		return dup_count;
	}
}

Please Enter the Duplicate Array size  : 11

Enter Duplicate Array 11 elements : 4 22 19 4 22 11 4 19 9 19 99

The Total Number of Duplicates  = 5