find the missing and no duplicate number in an array 1 to 10

There are multiple way to find the missing and no duplicate number in an array 1 to 10.

Using Boolean validate() method :-

First we take one input array from 1 to 10.
Now iterate this array number from for loop.
Create one boolean validate method, pass array data and total data from index i
Inside validate method its compare(arr[j] == k) array data with index.
if equals its return true else false.
Now depend on the status its print missing number.

Using a Mathematical Method :-

First we take one input array from 1 to 10.
Sum the first n natural numbers by using the formula sum=n*(n+1)/2.
To keep the total of the array’s items, create the variable actualSumValue.
Now iterate this array number from for loop.
Here actualSumValue should be updated to actualSumValue= actualSumValue.+ b[i].
Print (sum – actualSumValue) to give missing number.

				
					public class FindMissingNumber {
	public static void main(String[] args) {
		
		// Using Boolean validate() method
		int a[] = { 1, 2, 4, 5, 6, 7, 8, 9, 10 };
		for (int i = 1; i < a.length; i++) {
			boolean isStatus = validate(a, i);
			if (isStatus == false) {
				System.out.println("from Boolean validate() method to find the missing number:- " + i);
				break;
			}
		}
		// Using a Mathematical Method
		int b[] = { 1, 2, 4, 5, 6, 7, 8, 9, 10 };
		int sum = (10) * (10 + 1) / 2; // formula sum=n*(n+1)/2
		int actualSumValue = 0;
		for (int i = 0; i < b.length; i++) {
			actualSumValue = actualSumValue + b[i];
		}
		System.out.println(
				"from Mathematical Method to find the missing number in second way:- " + (sum - actualSumValue));
	}

	public static boolean validate(int arr[], int k) {
		for (int j = 0; j < arr.length; j++) {
			if (arr[j] == k) {
				return true;
			}
		}
		return false;
	}
}

Output :-
from Boolean validate() method to find the missing number:- 3
from Mathematical Method to find the missing number in second way:- 3