Java Interview Programs - Part 3

18) Find sum of elements in an array using recursion? 

class SumOfArray {
	public static void main (String[] args) {
    int[] arr = {1,2,3,4,5};
    int len = arr.length;
    System.out.println("The addition is: " + addition(arr, len));
	}
  
  public static int addition(int[] arr, int len){
    if(len == 0){
      return 0;
    }
    return arr[len-1] + addition(arr, len-1);
 }
}

19) Write a java program to find duplicate elements in an array?

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public class FindDuplicatesInArray { public static void main(String[] args) { int[] arr = {3,4,6,6,3,4}; for (int i = 0; i < arr.length; i++) { for (int j = i + 1; j < arr.length; j++) { if (arr[i] == (arr[j])) { System.out.println("Found duplicate " + arr[i]); } } } } }

Output:
Found duplicate 3
Found duplicate 4
Found duplicate 6

20) Find largest number in an array

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import java.util.ArrayList; public class FindMax { public static int max; public static void main(String[] args) { int[] arr = {3,14,16,17,3,4}; for (int i = 0; i < arr.length-1; i++) { if(arr[i]>arr[i+1]) { max = arr[i]; } } System.out.println(max); } }

Output: 17

21) To check equality of 2 arrays

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public class ArrayEquals { public static int max; public static boolean isEquals = true; public static void main(String[] args) { int[] arr1 = { 3, 14, 16, 17, 3, 4 }; int[] arr2 = { 3, 14, 16, 17, 3, 4, 3}; if (arr1.length == arr2.length) { for (int i = 0; i < arr1.length - 1; i++) { if (arr1[i] != arr2[i]) { System.out.println("Both arrays are not Equal"); isEquals = false; break; } } if (isEquals) System.out.println("Both arrays are Equal"); } else { System.out.println("Both arrays are not Equal"); } } }

Output: Both arrays are not Equal

22) Find third largest number in array

public class Xlargest {

 public static void main(String[] args) {

  int which_largest = 3;

  int[] arr = { 3, 14, 6, 17, 5, 4 };
  
  //Binary search logic
  for (int i = 0; i < arr.length; i++) {
   for (int j = 0; j < arr.length - 1; j++) {

    if (arr[j] > arr[j + 1]) {
     int temp = arr[j];
     arr[j] = arr[j + 1];
     arr[j + 1] = temp;
    }
   }
  }

  //Printing X largest value
  System.out.println(arr[arr.length - which_largest]);
 }
}

23) Reverse Array

public class ReverseArray {

 public static void main(String[] args) {

  ReverseArray obj = new ReverseArray();
  int[] arr = { 1, 2, 3, 4, 5, 6 };
  System.out.println("Before : ");
  obj.printArray(arr);
  obj.reverseArray(arr, 0, arr.length - 1);
  System.out.println("After : ");
  obj.printArray(arr);

 }

 public void reverseArray(int[] arr, int start, int end) {

  while (start < end) {
   int temp = arr[start];
   arr[start] = arr[end];
   arr[end] = temp;

   start = start + 1;
   end = end - 1;
  }

 }

 public void printArray(int[] arr) {
  for (int i = 0; i < arr.length; i++) {
   System.out.print(arr[i] + " ");
  }
 }

}

Output: 654321

24) Find second highest number in an array. 

class SecondHighest{
public static void main (String[] args) {
    int[] arr = {5,8,2,9,10};
    System.out.print(secondMax(arr));
}

public static int secondMax(int[] arr) {
    int max = arr[0];
    int smax = arr[0];
    
    for(int i = 0; i < arr.length; i++){
      if(arr[i] > max){
        max = arr[i];
      }
      
      if(arr[i] < max && arr[i] > smax)
        smax = arr[i];
    }
    return sMax;
   }
}

Output: 9

25) Find common elements in two different arrays

public class CommonElementArrays {

 public static void main(String[] args) {

  int[] arr = {1,2,3,4,5,6};
  int[] arr1 = {8,6,4,9,2};
  
  for(int i=0;i<arr.length;i++) {
   
   for (int j = 0; j < arr1.length; j++) {
    
    if (arr[i] == arr1[j]) { 
   
     System.out.println(arr[i]);
    }
   }
  }
 }
}

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