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Top 19 essential java program for an interview

Below are the set of 19 essential java program for an interview, hope you also referred our pervious post for java program.

Write a java program to Add two Matrix

package com.onurdesk.arraymatrix.programs;

import java.util.*;

class AddTwoMatrix {
	int m, n;
	int first[][] = new int[m][n];
	int second[][] = new int[m][n];

	AddTwoMatrix(int[][] first, int[][] second, int m, int n) {
		this.first = first;
		this.second = second;
		this.m = m;
		this.n = n;
	}

	public static void main(String[] args) {
		int m, n, c, d;

		Scanner in = new Scanner(System.in);

		System.out.println("Enter the number of rows and columns of matrix");
		m = in.nextInt();
		n = in.nextInt();

		int first[][] = new int[m][n];
		int second[][] = new int[m][n];

		System.out.println("Enter the elements of first matrix");

		for (c = 0; c < m; c++) {
			for (d = 0; d < n; d++) {
				first[c][d] = in.nextInt();
			}
		}

		System.out.println("Enter the elements of second matrix");

		for (c = 0; c < m; c++) {
			for (d = 0; d < n; d++) {
				second[c][d] = in.nextInt();
			}
		}

		System.out.println("\nElements of First matrix is : ");

		for (c = 0; c < m; c++) {
			for (d = 0; d < n; d++) {
				System.out.print(first[c][d] + "\t");
			}
			System.out.println();
		}

		System.out.println("\nElements of Second matrix is : ");

		for (c = 0; c < m; c++) {
			for (d = 0; d < n; d++) {
				System.out.print(second[c][d] + "\t");
			}
			System.out.println();
		}

		AddTwoMatrix a = new AddTwoMatrix(first, second, m, n);
		// call by reference
		a.addmatrix(a); // Passing Object
	}

	// Function for Adding two matrix and storing in third matrix
	public void addmatrix(AddTwoMatrix a) {
		int c, d;
		int sum[][] = new int[a.m][a.n];

		for (c = 0; c < a.m; c++) {
			for (d = 0; d < a.n; d++) {
				sum[c][d] = a.first[c][d] + a.second[c][d];
			}
		}

		System.out.println("\nSum of the two matrices is : ");

		for (c = 0; c < a.m; c++) {
			for (d = 0; d < a.n; d++) {
				System.out.print(sum[c][d] + "\t");
			}
			System.out.println();
		}
	}
}
Top 19 essential  java program for an interview

Write a java program of Array of Arrays in java.

package com.onurdesk.arraymatrix.programs;
class ArrayOfArraysAnimalDemo
{
    public static void main(String[] args)
    {
        String[][] animals = {{"DanaDog", "WallyDog", "JessieDog", "AlexisDog", "LuckyDog"}, {"BibsCat", "DoodleCat", "MillieCat", "SimonCat"}, {"ElyFish", "CloieFish", "GoldieFish", "OscarFish", "ZippyFish", "TedFish"}, {"RascalMule", "GeorgeMule", "GracieMule", "MontyMule", "BuckMule", "RosieMule"}};

        for (int i = 0; i < animals.length; i++)
        {
            System.out.print(animals[i][0] + ": ");

            for (int j = 1; j < animals[i].length; j++)
            {
                System.out.print(animals[i][j] + " ");
            }

            System.out.println();
        }
    }
}
Top 19 essential  java program for an interview

Write a java program to perform operation on Array.

package com.onurdesk.arraymatrix.programs;
class ArrayOperations
{
    public static void main(String[] args)
    {
        double[] myList = {1.9, 2.9, 3.4, 3.5};

        // Print all the array elements
        for (int i = 0; i < myList.length; i++)
        {
            System.out.println(myList[i] + " ");
        }
        // Summing all elements
        double total = 0;
        for (int i = 0; i < myList.length; i++)
        {
            total += myList[i];
        }

        System.out.println("Total is " + total);

        // Finding the largest element
        double max = myList[0];
        for (int i = 1; i < myList.length; i++)
        {
            if (myList[i] > max)
                max = myList[i];
        }

        System.out.println("Max is " + max);
    }
}
Top 19 essential  java program for an interview

Write a java program to sort an Array.

package com.onurdesk.arraymatrix.programs;
import java.util.Arrays;

class ArraySort
{
    // This program is the example of  array sorting
    public static void main(String[] args)
    {
        // TODO Auto-generated method stub
        // initializing unsorted  array
        String iArr[] = {"Programming", "Hub", "Alice", "Wonder", "Land"};

        // sorting array
        Arrays.sort(iArr);

        // let us print all the elements available in list
        System.out.println("The sorted array is:");
        for (int i = 0; i < iArr.length; i++)
        {
            System.out.println(iArr[i]);
        }
    }
}
Top 19 essential  java program for an interview

Write a java program to sum and average of Array.

package com.onurdesk.arraymatrix.programs;
import java.io.*;

class ArrayAverage
{
    public static void main(String[] args)
    {
        //define an array
        int[] numbers = new int[]{10, 20, 15, 25, 16, 60, 100};

        int sum = 0;

        for (int i = 0; i < numbers.length; i++)
        {
            sum = sum + numbers[i];
        }

        double average = sum / numbers.length;
        System.out.println("Sum of array elements is : " + sum);
        System.out.println("Average value of array elements is : " + average);
    }
}

Write a java program to take elements of array and print the array.

package com.onurdesk.arraymatrix.programs;
import java.util.*;

class ArrayBasic
{
    public static void main(String[] args)
    {
        int[] arr;
        int size, i;

        Scanner sc = new Scanner(System.in);

        System.out.println("Enter size of array");
        size = sc.nextInt();

        arr = new int[size];

        System.out.println("\nEnter array elements");
        for (i = 0; i < size; i++)
        {
            arr[i] = sc.nextInt();
        }

        System.out.println("\nElements in the Array are : ");
        for (i = 0; i < size; i++)
        {
            System.out.print(arr[i] + " ");
        }
    }
}

Write a java program to create and display Matrix.

package com.onurdesk.arraymatrix.programs;
import java.util.Scanner;
 
 class Matrix_Create {
 
 Scanner scan;
 int matrix[][];
 int row, column;
 
 void create() {
  
  scan = new Scanner(System.in);
  
  System.out.println("Matrix Creation");
  
  System.out.println("\nEnter number of rows :");
  row = Integer.parseInt(scan.nextLine());
  
  System.out.println("Enter number of columns :");
  column = Integer.parseInt(scan.nextLine());
  
  matrix = new int[row][column];
  System.out.println("Enter the data :");
 
  for(int i=0; i<row ; i++) {
   
   for(int j=0; j
    <column ; j++) {
    
    matrix[i][j] =scan.nextInt();
     }
  }
 }
 
 void display() {
  
  System.out.println("\nThe Matrix is :");
  
  for(int i=0; i <row ; i++) {
   
   for(int j=0; j <column ; j++) {
    
    System.out.print("\t" + matrix[i][j]);
   }
   System.out.println();
  }
 }
}
 
  class CreateAndDisplayMatrix {
 
 public static void main(String
     args[]) {
  
  Matrix_Create obj=new Matrix_Create();
  
  obj.create();
  obj.display();
 }
}

Write a java program to create and display Double Matrix.

package com.onurdesk.arraymatrix.programs;
import java.util.*;
import java.text.DecimalFormat;
//like us on facebook : https://facebook.com/onurdesk
class DoubleMatrix
{
    public static void main(String[] args)
    {
        double[][] a;
        double[] s;
        int row, col, k = 0, i, j;
        double sum = 0.0;

        DecimalFormat f = new DecimalFormat("##.####");
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter size of row and column");
        row = sc.nextInt();
        col = sc.nextInt();

        a = new double[row][col];
        s = new double[col];

        System.out.println("Enter elements of matrix");
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
                a[i][j] = sc.nextDouble();
            }
        }

        System.out.println("Double Matrix is : ");
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
                System.out.print(" " + a[i][j]);
            }
            System.out.println();
        }

        //sum of the elements of double matrix

        for (i = 0; i < col; i++)
        {
            for (j = 0; j < row; j++)
            {
                sum = sum + a[j][i];
            }
            s[k] = sum;
            k++;
            sum = 0;
        }

        for (i = 0; i < col; i++)
        {
            System.out.println("Sum of Column " + (i + 1) + " is : " + f.format(s[i]));
        }
    }
}

Write a java program to Display array using For Each loop.

package com.onurdesk.arraymatrix.programs;
class DisplayArrayForEach
{
    public static void main(String[] args)
    {
        double[] myList = {1.9, 2.9, 3.4, 3.5};

        // Print all the array elements
        for (double element : myList)
        {
            System.out.println(element);
        }
    }
}

Write a java program to Pass Arrays to function.

package com.onurdesk.arraymatrix.programs;
import java.util.*;
class PassingArraystoFunction 
{
    public static void main(String[] args) 
    {
        int[] a;
        int size;
        
        Scanner sc = new Scanner(System.in);
        
        System.out.println("Enter size of array");
        size = sc.nextInt();
        
        a = new int[size];
        
        System.out.println("Enter elements in the array");
        for(int i = 0 ;i < size; i++)
        {
            a[i] = sc.nextInt();
        }

        System.out.println("The Elements of the array are : ");
        for(int i = 0 ;i < size; i++)
        {
            System.out.print(a[i] + " ");
        }

        //Passing array to the function
        addElements(a, size);
    }
    
    public static void addElements(int[] a , int size)
    {
        int sum = 0;
        
        for(int i = 0; i < size; i++)
        {
            sum += a[i];
        }

        System.out.println("\nSum of the elements of arrays is : "+sum);
    }
}

Write a java program to find the closest value of a number in an Array.

package com.onurdesk.arraymatrix.programs;
import java.util.*;

class ClosestValue
{
    public static void main(String[] args)
    {
        int a[];
        int find;
        int closest = 0;

        Scanner sc = new Scanner(System.in);

        System.out.println("Enter size of array");
        int size = sc.nextInt();

        a = new int[size];

        System.out.println("Enter numbers in array");
        for (int i = 0; i < size; i++)
        {
            a[i] = sc.nextInt();
        }

        System.out.println("Numbers are : ");
        for (int i = 0; i < size; i++)
        {
            System.out.print(a[i] + " ");
        }

        System.out.println();
        System.out.println("Enter Number to find closest value");
        find = sc.nextInt();

        int distance = Math.abs(closest - find);

        for (int i : a)
        {
            int distanceI = Math.abs(i - find);
            if (distance > distanceI)
            {
                closest = i;
                distance = distanceI;
            }
        }

        System.out.println("Closest Value is : " + closest);
    }

}

Write a java program for Magic Matrix.

package com.onurdesk.arraymatrix.programs;
import java.io.*;

class MagicMatrix
{
    public static void main(String args[]) throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter the size of the matrix : ");
        int n = Integer.parseInt(br.readLine());

        if (n > 5)
            System.out.println("Enter a number between 1 to 5 ");
        else
        {
            int A[][] = new int[n][n]; // Creating the Magic Matrix
            int i, j, k, t;
         
            /*Initializing every cell of the matrix with 0 */
            for (i = 0; i < n; i++)
            {
                for (j = 0; j < n; j++)
                {
                    A[i][j] = 0;
                }
            }

            /* When the size of the matrix is Odd */
            if (n % 2 != 0)
            {
                i = 0;
                j = n / 2;
                k = 1;
                while (k <= n * n)
                {
                    A[i][j] = k++;
                    i--; // Making one step upward
                    j++; // Moving one step to the right

                    if (i < 0 && j > n - 1) // Condition for the top-right corner element
                    {
                        i = i + 2;
                        j--;
                    }

                    if (i < 0) // Wrapping around the row if it goes out of boundary
                        i = n - 1;

                    if (j > n - 1) // Wrapping around the column if it goes out of boundary
                        j = 0;

                    if (A[i][j] > 0) // Condition when the cell is already filled
                    {
                        i = i + 2;
                        j--;
                    }
                }
            }
            /* When the size of the matrix is even */
            else
            {
                k = 1;
             
                /* Filling the matrix with natural numbers from 1 till n*n */
                for (i = 0; i < n; i++)
                {
                    for (j = 0; j < n; j++)
                    {
                        A[i][j] = k++;
                    }
                }

                j = n - 1;

                for (i = 0; i < n / 2; i++)
                {
                    /* swapping corner elements of primary diagonal */
                    t = A[i][i];
                    A[i][i] = A[j][j];
                    A[j][j] = t;
                 
                    /* swapping corner elements of secondary diagonal */
                    t = A[i][j];
                    A[i][j] = A[j][i];
                    A[j][i] = t;

                    j--;
                }
            }

            /* Printing the Magic matrix */
            System.out.println("The Magic Matrix of size " + n + "x" + n + " is:");
            for (i = 0; i < n; i++)
            {
                for (j = 0; j < n; j++)
                {
                    System.out.print(A[i][j] + "\t");
                }
                System.out.println();
            }
        }
    }
}

Write a java program to perform Matrix Multiplication.

package com.onurdesk.arraymatrix.programs;
import java.util.Scanner;

class MatrixMultiplication
{
    public static void main(String args[])
    {
        int m, n, p, q, sum = 0, c, d, k;

        Scanner in = new Scanner(System.in);
        System.out.println("Enter the number of rows and columns of first matrix");
        m = in.nextInt();
        n = in.nextInt();

        int first[][] = new int[m][n];

        System.out.println("Enter the elements of first matrix");

        for (c = 0; c < m; c++)
        {
            for (d = 0; d < n; d++)
            {
                first[c][d] = in.nextInt();
            }
        }

        System.out.println("Enter the number of rows and columns of second matrix");
        p = in.nextInt();
        q = in.nextInt();

        if (n != p)
            System.out.println("Matrices with entered orders can't be multiplied with each other.");
        else
        {
            int second[][] = new int[p][q];
            int multiply[][] = new int[m][q];

            System.out.println("Enter the elements of second matrix");

            for (c = 0; c < p; c++)
            {
                for (d = 0; d < q; d++)
                {
                    second[c][d] = in.nextInt();
                }
            }

            for (c = 0; c < m; c++)
            {
                for (d = 0; d < q; d++)
                {
                    for (k = 0; k < p; k++)
                    {
                        sum = sum + first[c][k] * second[k][d];
                    }

                    multiply[c][d] = sum;
                    sum = 0;
                }
            }

            System.out.println("Product of entered matrices:-");

            for (c = 0; c < m; c++)
            {
                for (d = 0; d < q; d++)
                {
                    System.out.print(multiply[c][d] + "\t");
                }

                System.out.print("\n");
            }
        }
    }
}

Writ a java program to perform operations on Matrix.

package com.onurdesk.arraymatrix.programs;
import java.util.Scanner; 
 
public class Matrices { 
 
   public static void main(String[] args) { 
     
       Scanner scanner = new Scanner(System.in); 
        
       System.out.print("Enter number of rows: "); 
       int rows = scanner.nextInt(); 
        
       System.out.print("Enter number of columns: "); 
       int columns = scanner.nextInt(); 
        
       System.out.println(); 
       System.out.println("Enter first matrix"); 
       int[][] a = readMatrix(rows, columns); 
        
       System.out.println(); 
       System.out.println("Enter second matrix"); 
       int[][] b = readMatrix(rows, columns); 
        
       int[][] sum = add(a, b); 
       int[][] difference1 = subtract(a, b); 
       int[][] difference2 = subtract(b, a); 
        
       System.out.println(); 
       System.out.println("A + B ="); 
       printMatrix(sum); 
        
       System.out.println(); 
       System.out.println("A - B ="); 
       printMatrix(difference1); 
        
       System.out.println(); 
       System.out.println("B - A ="); 
       printMatrix(difference2); 
   } 
 
   public static int[][] readMatrix(int rows, int columns) { 
     
       int[][] result = new int[rows][columns]; 
       Scanner s = new Scanner(System.in); 
        
       for (int i = 0; i < rows; i++) { 
         
           for (int j = 0; j < columns; j++) { 
             
               result[i][j] = s.nextInt(); 
                
           } 
       } 
       return result; 
   } 
 
   public static int[][] add(int[][] a, int[][] b) { 
     
       int rows = a.length; 
       int columns = a[0].length; 
       int[][] result = new int[rows][columns]; 
        
       for (int i = 0; i < rows; i++) { 
         
           for (int j = 0; j < columns; j++) { 
             
               result[i][j] = a[i][j] + b[i][j]; 
                
           } 
       } 
       return result; 
   } 
 
   public static int[][] subtract(int[][] a, int[][] b) { 
     
       int rows = a.length; 
       int columns = a[0].length; 
       int[][] result = new int[rows][columns]; 
        
       for (int i = 0; i < rows; i++) { 
         
           for (int j = 0; j < columns; j++) { 
             
               result[i][j] = a[i][j] - b[i][j]; 
                
           } 
       } 
       return result; 
   } 
 
   public static void printMatrix(int[][] matrix) { 
     
       int rows = matrix.length; 
       int columns = matrix[0].length; 
        
       for (int i = 0; i < rows; i++) { 
         
           for (int j = 0; j < columns; j++) { 
             
               System.out.print(matrix[i][j] + "  "); 
                
           } 
           System.out.println(); 
       } 
   } 
}

Writ a java program for Merge two array.

package com.onurdesk.arraymatrix.programs;
class MergeArrayDemo
{
 public static void main(String args[])
 {
  Integer a[]={1,2,3,4};
  Integer b[]={5,6,7,0};
  Integer[] both = concat(a, b);
  
  System.out.print("\nFirst  Array : ");
  for(int i=0;i<a.length;i++)
  {
   System.out.print(a[i]+"\t");
  }

  System.out.print("\nSecond Array : ");
  for(int i=0;i<b.length;i++)
  {
   System.out.print(b[i]+"\t");
  }

  System.out.print("\nMerged Array : ");
  for(int i=0;i<both.length;i++)
  {
   System.out.print(both[i]+"\t");
  }
 }

 public static Integer[] concat(Integer[] a, Integer[] b)
 {
  int aLen = a.length;
  int bLen = b.length;
  Integer[] c= new Integer[aLen+bLen];
  System.arraycopy(a, 0, c, 0, aLen);
  System.arraycopy(b, 0, c, aLen, bLen);
  return c;
 }
}

Write a java program to find middle value of array.

package com.onurdesk.arraymatrix.programs;
import java.util.*;

class MiddleValue
{
    public static void main(String args[])
    {
        int[] a;
        int i, j, n, sum = 0, swap, size;

        double t;
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter size of array");
        size = sc.nextInt();

        a = new int[size];

        System.out.println("Enter numbers ");
        for (i = 0; i < size; i++)
        {
            a[i] = sc.nextInt();
        }

        System.out.println("Numbers are : ");
        for (i = 0; i < size; i++)
        {
            System.out.print(a[i] + " ");
        }

        //Sorting
        for (i = 0; i < (size - 1); i++)
        {
            for (j = 0; j < (size - i - 1); j++)
            {
                if (a[j] > a[j + 1])
                {
                    swap = a[j];
                    a[j] = a[j + 1];
                    a[j + 1] = swap;
                }
            }
        }

        System.out.println("\nNumbers in sorted order : ");
        for (i = 0; i < size; i++)
        {
            System.out.print(a[i] + " ");
        }

        //Finding the Middle Value
        if (size % 2 == 0)
        {
            n = (size + 1) / 2;
            t = (a[n] + a[n - 1]) / 2.0;
            System.out.println("\nMiddle Value is : " + t);
        }

        else
        {
            System.out.println("\nMiddle Value is : " + a[size / 2]);
        }

    }
}

Write a java program for Mirror Matrix.

package com.onurdesk.arraymatrix.programs;
import java.util.*;

class MirrorMatrix
{
    public static void main(String[] args)
    {
        int row, column;
        Scanner in = new Scanner(System.in);

        System.out.print("Enter number of rows for matrix :");
        row = in.nextInt();
        System.out.print("Enter number of rows for matrix :");
        column = in.nextInt();

        int matrix[][] = new int[row][column];

        System.out.println("Enter matrix : ");

        for (int i = 0; i < row; i++)
        {
            for (int j = 0; j < column; j++)
            {
                matrix[i][j] = in.nextInt();
            }
        }

        System.out.println("Mirror matrix : ");

        for (int i = 0; i < row; i++)
        {
            for (int j = column - 1; j >= 0; j--)
            {
                System.out.print(matrix[i][j] + "\t");
            }

            System.out.println("");
        }
    }
}

Write a java program to find a Missing number in an array.

class MissingNumberArray
{
    public static int count = 0;
    public static int position = 0;
    public static boolean flag = false;

    public static void main(String[] args)
    {
        int a[] = {0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 20, 21, 23};

        findMissingNumbers(a, position);
    }

    private static void findMissingNumbers(int a[], int position)
    {
        if (position == a.length - 1)
            return;

        for (; position < a[a.length - 1]; position++)
        {
            if ((a[position] - count) != position)
            {
                System.out.println("Missing Number: " + (position + count));
                flag = true;
                count++;
                break;
            }
        }

        if (flag)
        {
            flag = false;
            findMissingNumbers(a, position);
        }
    }
}

Write a java program for Multidimensional Array.

package com.onurdesk.arraymatrix.programs;
class MultiDimArrayExample
{
    public static void main(String[] args)
    {
        String[][] names = {{"Mr. ", "Mrs. ", "Ms. "}, {"Smith", "Jones"}};
        // Mr. Smith
        System.out.println(names[0][0] + names[1][0]);
        // Ms. Jones
        System.out.println(names[0][2] + names[1][1]);
    }
}

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Onurdesk is a technical platform based primarily on Spring, Java, and Nodejs ecosystem app creation. We write tutorials and manuals concentrating extensively on realistic and real-life usage cases.

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