Java Interview Questions - Part 3

Coding Questions - Arrays

1. Array Sum:

   Question: Write a Java program to find the sum of all elements in an array.

   Answer:

   
   public class ArraySum {
       public static void main(String[] args) {
           int[] numbers = {1, 2, 3, 4, 5};
           int sum = 0;
   
           for (int num : numbers) {
               sum += num;
           }
   
           System.out.println("Sum of the array elements: " + sum);
       }
   }
           

   Description: This program initializes an array and calculates the sum of its elements using a for-each loop.

2. Find Maximum Element:

   Question: Write a Java program to find the maximum element in an array.

   Answer:

   
   public class MaxElement {
       public static void main(String[] args) {
           int[] numbers = {10, 5, 8, 20, 15};
           int max = numbers[0];
   
           for (int num : numbers) {
               if (num > max) {
                   max = num;
               }
           }
   
           System.out.println("Maximum element in the array: " + max);
       }
   }
           

   Description: This program iterates through the array to find the maximum element.

3. Array Rotation:

   Question: Write a Java program to rotate elements of an array to the left by a given number of positions.

   Answer:

   
   public class ArrayRotation {
       public static void main(String[] args) {
           int[] numbers = {1, 2, 3, 4, 5};
           int rotations = 2;
   
           for (int i = 0; i < rotations; i++) {
               int temp = numbers[0];
               for (int j = 0; j < numbers.length - 1; j++) {
                   numbers[j] = numbers[j + 1];
               }
               numbers[numbers.length - 1] = temp;
           }
   
           System.out.println("Array after " + rotations + " left rotations: " + Arrays.toString(numbers));
       }
   }
           

   Description: This program rotates the elements of an array to the left by the specified number of positions using a temporary variable.

4. Array Intersection:

   Question: Write a Java program to find the intersection of two arrays.

   Answer:

   
   import java.util.Arrays;
   import java.util.HashSet;
   import java.util.Set;
   
   public class ArrayIntersection {
       public static void main(String[] args) {
           int[] array1 = {1, 2, 3, 4, 5};
           int[] array2 = {3, 4, 5, 6, 7};
   
           Set<Integer> set1 = new HashSet<>(Arrays.asList(array1));
           Set<Integer> set2 = new HashSet<>(Arrays.asList(array2));
   
           set1.retainAll(set2);
   
           int[] intersection = set1.stream().mapToInt(Integer::intValue).toArray();
   
           System.out.println("Intersection of the arrays: " + Arrays.toString(intersection));
       }
   }
           

   Description: This program uses sets to find the intersection of two arrays, converting the result back to an array.

5. Array Reversal:

   Question: Write a Java program to reverse the elements of an array.

   Answer:

   
   import java.util.Arrays;
   
   public class ArrayReversal {
       public static void main(String[] args) {
           int[] numbers = {1, 2, 3, 4, 5};
   
           for (int i = 0; i < numbers.length / 2; i++) {
               int temp = numbers[i];
               numbers[i] = numbers[numbers.length - i - 1];
               numbers[numbers.length - i - 1] = temp;
           }
   
           System.out.println("Reversed array: " + Arrays.toString(numbers));
       }
   }
           

   Description: This program reverses the elements of an array using a two-pointer approach.