Java Programs asked in Interviews

// Java program to Convert String into reverse  String 

public static void main(String[] args) {

String a = "This is my country , And I love my Country";
String b="";
for (int i = a.length()-1; i > 0; i--) {

b+=a.charAt(i);
}
System.out.println(b +"\n" +a);
}
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// Java program to reverse integer array 

public static void main(String[] args) {
int[] inputArray = { 2, 4, 6, 3, 8, 9, 44, 3 ,22};
int [] OutputArray = new int [inputArray .length];  // define lenght of int array
int j =0;  // define counter for OutputArray 
// take element from end of  inputArray and add in front of outputArray
for (int i =a.length-1; i>0;i-- ){
b[j]= a[i];

System.out.println(a[i]+"**"+b[j]);
j++; // Increase a counter 
}


}
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// Java program to reverse integer array with binary 

*********************************************************************************

//// Java program to reverse words of String 
// input =>"This is my country And I love my Country";
//output => "sihT si ym yrtnuoc dnA I evol ym yrtnuoC"

public static void main(String[] args) {
String inputString = "This is my country And I love my Country";  //input string

String[] words = inputString.split(" "); //split words, now -->This , is , my , country,..etc

String reverseString = ""; // get output in this.

// first loop to get get each words one by one from string 
for (int i = 0; i < words.length; i++) {
String word = words[i]; //initi, word  contain -"This" in next iteration it's "is " & so on

String reverseWord = ""; // get a output (reverse word)

//second loop is for to reverse a word
for (int j = word.length() - 1; j >= 0; j--) {
reverseWord = reverseWord + word.charAt(j); //append chars in reverse manner
}

reverseString = reverseString + reverseWord + " "; //appends words as process from inner loop
}

System.out.println(inputString);

System.out.println(reverseString);

}

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// Prefix and post fix 

public static void main(String[] args){
int x;
int a = 100;
System.out.println(a-- +"==="+--a);
                                          //100   99           98
                          //         values   postfix    ,prefix 99 is became 98
x=a-- - --a;
System.out.println(x); //output is -->2
}

}

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//To Find Duplicate Elements In An Array 

 public static void main(String[] args)

    {

        String[] strArray = {"abc", "def", "mno", "xyz", "pqr", "xyz", "def"};

        for (int i = 0; i < strArray.length-1; i++) //to take 1 element from array

        {

            for (int j = i+1; j < strArray.length; j++)//compare all the element in array one by one

            {

                if( (strArray[i].equals(strArray[j])) && (i != j) )

//to avoid outOfIndex Error

                {

                    System.out.println("Duplicate Element is : "+strArray[j]);

                }

            }

        }

    }   




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// Find Second Largest Number In An Integer Array :

public static void main(String[] args) {

        int firstLargest, secondLargest;

       if(input[0] > input[1])  //Checking first two elements of input array

        {

            //If first element is greater than second element

            firstLargest = input[0];

            secondLargest = input[1];

        }

        else

        {

            //If second element is greater than first element

            firstLargest = input[1];

            secondLargest = input[0];

        }

        //Checking remaining elements of input array

        for (int i = 2; i < input.length; i++)

        {

            if(input[i] > firstLargest)

            {

                //If element at 'i' is greater than 'firstLargest'

                secondLargest = firstLargest;

                firstLargest = input[i];

            }

            else if (input[i] < firstLargest && input[i] > secondLargest)

            {

                //If element at 'i' is smaller than 'firstLargest' and greater than 'secondLargest'

                secondLargest = input[i];

            }

        }

System.out.println(secondLargest );

     }

*********************************************************************************

// Sorting the integer array 

public static void main(String[] args) {

int[] inputArray = { 1, 2, 4, 6, 3, 8, 9, 44, 3, 22 };

        int temp, pos;

        for (int i = 0; i < inputArray.length - 1; i++) //loop for taking first element 

        {

            pos = i;  // initializing pos variable within for loop so every-time it is incremented

            //finding the position of smallest element between (i+1)th element and last element

            for (int j = i+1; j < inputArray.length; j++)

            {

                if(inputArray[j] < inputArray[pos] ) // condition to find smallest element 

                {

                    pos = j;

                }

            }

            //Swapping inputArray[i] and inputArray[pos]

            temp = inputArray[i];

            inputArray[i] = inputArray[pos];

            inputArray[pos] = temp;

        }

        for (int i = 0; i < inputArray.length; i++)

        {

            System.out.print(inputArray[i] + " ");

        }

        System.out.println();

    }

*********************************************************************************

// Find a continues sub array whose sum is equal to inputNumber

public static void main(String[] args) {

int[] inputArray = { 1, 2, 4, 6, 3, 8, 9, 44, 3, 22 };

int inputNumber = 15;

int sum = 0; // Initializing 'sum' to 0

// Iterating through 'inputArray'

for (int i = 0; i < inputArray.length; i++) {

sum = inputArray[i];  // Assigning inputArray[i] to 'sum'

for (int j = i + 1; j < inputArray.length; j++) {

// Adding inputArray[j] to 'sum'

sum = sum + inputArray[j];

// If 'sum' is equal to 'inputNumber' then printing the sub array

if (sum == inputNumber) {

System.out.println("Continuous sub array of "

+ Arrays.toString(inputArray) + " whose sum is "

+ inputNumber + " is ");

                  //print sub array from i element to j element which satisfy a condition 

for (int k = i; k <= j; k++) {

System.out.print(inputArray[k] + " ");

}

System.out.println();

}

// if 'sum' is smaller than 'inputNumber', continue the loop

else if (sum < inputNumber) {

continue;

}

// if 'sum' is greater than 'inputNumber', then break the loop

else if (sum > inputNumber) {

break;

}

}

}

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// Reverse The String With Preserving The Position Of Spaces :

public static void main(String[] args) {

String inputString = "Hi this is good tested Nagard";

         

        char[] inputStringArray = inputString.toCharArray();//Converting inputString to char array 'inputStringArray'

         

        //Defining a new char array 'resultArray' with same size as inputStringArray

         

        char[] resultArray = new char[inputStringArray.length];

         

        //First for loop :

        //For every space in the 'inputStringArray',

        //we insert spaces in the 'resultArray' at the corresponding positions

         

        for (int i = 0; i < inputStringArray.length; i++)

        {

            if (inputStringArray[i] == ' ')

            {

                resultArray[i] = ' ';

            }

        }

         

        //Initializing 'j' with length of resultArray

         

        int j = 0;

                 

        //Second for loop :

        //we copy every non-space character of inputStringArray

        //from first to last at 'j' position of resultArray

         

        for (int i = inputStringArray.length-1; i >0; i--)

        {

            if (inputStringArray[i] != ' ')

            {

                //If resultArray already has space at index j then decrementing 'j'

                 

                if(resultArray[j] != ' ')

                {

                   resultArray[j] = inputStringArray[i];

                }

                 

                               

                j++;

            }

        }

         

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//Find The Percentage Of Uppercase Letters, Lowercase Letters, Digits And Other Special Characters In A String

public static void main(String[] args) {


String inputString = "Hi My email id is Test@gmail.com 112 time appear";

 //Getting total no of characters in the given string

         

        int totalChars = inputString.length();

         

        //Initializing upperCaseLetters, lowerCaseLetters, digits and others with 0

         

        int upperCaseLetters = 0;

         

        int lowerCaseLetters = 0;

         

        int digits = 0;

         

        int others = 0;

         

        //Iterating through each character of inputString

         

        for (int i = 0; i < inputString.length(); i++)

        {

            char ch = inputString.charAt(i);

             

            //If ch is in uppercase, then incrementing upperCaseLetters

             

            if(Character.isUpperCase(ch))

            {

                upperCaseLetters++;

            }

             

            //If ch is in lowercase, then incrementing lowerCaseLetters

             

            else if(Character.isLowerCase(ch))

            {

                lowerCaseLetters++;

            }

             

            //If ch is a digit, then incrementing digits

             

            else if (Character.isDigit(ch))

            {

                digits++;

            }

             

            //If ch is a special character then incrementing others

             

            else

            {

                others++;

            }

        }

         

        //Calculating percentage of uppercase letters, lowercase letters, digits and other characters

         

        double upperCaseLetterPercentage = (upperCaseLetters * 100.0) / totalChars ;

         

        double lowerCaseLetterPercentage = (lowerCaseLetters * 100.0) / totalChars;

         

        double digitsPercentage = (digits * 100.0) / totalChars;

         

        double otherCharPercentage = (others * 100.0) / totalChars;

         

        DecimalFormat formatter = new DecimalFormat("##.##");

         

        //Printing percentage of uppercase letters, lowercase letters, digits and other characters

         

        System.out.println("In '"+inputString+"' : ");

         

        System.out.println("Uppercase letters are "+formatter.format(upperCaseLetterPercentage)+"% ");

         

        System.out.println("Lowercase letters are "+formatter.format(lowerCaseLetterPercentage)+"%");

         

        System.out.println("Digits Are "+formatter.format(digitsPercentage)+"%");

         

        System.out.println("Other Characters Are "+formatter.format(otherCharPercentage)+"%");

         

 }

}

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// Creation Of Matrix In Java




Scanner sc = new Scanner(System.in);

         

        System.out.println("Enter The Number Of Rows");

         

        int row = sc.nextInt();

         

        System.out.println("Enter The Number Of Columns");

         

        int cols = sc.nextInt();

         

        //defining 2D array to hold matrix data

         

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

         

        System.out.println("Enter Matrix Data");

         

        for (int i = 0; i < row; i++)

        {

            for (int j = 0; j < cols; j++)

            {

                matrix[i][j] = sc.nextInt();

            }

        }

         

        System.out.println("Your Matrix is : ");

         

        for (int i = 0; i < row; i++)

        {

            for (int j = 0; j < cols; j++)

            {

                System.out.print(matrix[i][j]+"\t");

            }

             

            System.out.println();

        }

  

*********************************************************************************

//Matrix Addition In Java

    

public static void main(String[] args) {


       Scanner sc = new Scanner(System.in); // Make ready compiler to ready from data 
     
       System.out.println("Enter The Number Of Rows");
     
       int row = sc.nextInt();
     
       System.out.println("Enter The Number Of Columns");
     
       int cols = sc.nextInt();
     
       int[][] matrix1 = new int[row][cols]; // Define matrix
     
       int[][] matrix2 = new int[row][cols];
     
       int[][] sum = new int[row][cols];
     
       System.out.println("Enter The Data For First Matrix :");
     
       for (int i = 0; i < row; i++)
       {
           for (int j = 0; j < cols; j++)
           {
               matrix1[i][j] = sc.nextInt();
           }
       }
     
       System.out.println("Enter The Data For Second Matrix :");
     
       for (int i = 0; i < row; i++)
       {
           for (int j = 0; j < cols; j++)
           {
               matrix2[i][j] = sc.nextInt();
           }
       }
     
     
       System.out.println("Sum = ");
     
       for (int i = 0; i < row; i++)
       {
           for (int j = 0; j < cols; j++)
           {
               sum[i][j] = matrix1[i][j] + matrix2[i][j];
             
               System.out.print(sum[i][j]+"\t");
           }
         
           System.out.println();
       }
*********************************************************************************
// Multiplication of Matrix 

 public static void main(String[] args)

    {

        Scanner sc = new Scanner(System.in);

         

        System.out.println("Enter The Number Of Rows In First Matrix");

         

        int rowsInFirst = sc.nextInt();

         

        System.out.println("Enter The Number Of Columns In First Matrix / Rows In Second Matrix");

         

        int colsInFirstRowsInSecond = sc.nextInt();

         

        System.out.println("Enter The Number Of Columns In Second Matrix");

         

        int colsInSecond = sc.nextInt();

         

        int[][] matrix1 = new int[rowsInFirst][colsInFirstRowsInSecond];

         

        int[][] matrix2 = new int[colsInFirstRowsInSecond][colsInSecond];

         

        int[][] product = new int[rowsInFirst][colsInSecond];

         

        System.out.println("Enter The Data For First Matrix :");

         

        for (int i = 0; i < rowsInFirst; i++)

        {

            for (int j = 0; j < colsInFirstRowsInSecond; j++)

            {

                matrix1[i][j] = sc.nextInt();

            }

        }

         

        System.out.println("Enter The Data For Second Matrix :");

         

        for (int i = 0; i < colsInFirstRowsInSecond; i++)

        {

            for (int j = 0; j < colsInSecond; j++)

            {

                matrix2[i][j] = sc.nextInt();

            }

        }

         

            

        System.out.println("Product = ");

         

        for (int i = 0; i < rowsInFirst; i++)

        {

            for (int j = 0; j < colsInSecond; j++)

            {

                for (int k = 0; k < colsInFirstRowsInSecond; k++)

                {

                    product[i][j] +=  matrix1[i][k] * matrix2[k][j];

                }

            }

        }

         

        for (int i = 0; i < rowsInFirst; i++)

        {

            for (int j = 0; j < colsInSecond; j++)

            {

                System.out.print(product[i][j]+"\t");

            }

             

            System.out.println();

        }

    }

*********************************************************************************
// Transpose of Matrix (Rows into col and col into rows)

  public static void main(String[] args)

    {

        Scanner sc = new Scanner(System.in);

         

        System.out.println("Enter The Number Of Rows");

         

        int rows = sc.nextInt();

         

        System.out.println("Enter The Number Of Columns");

         

        int cols = sc.nextInt();

         

        int[][] matrix = new int[rows][cols];

     

        int[][] transpose = new int[cols][rows];

         

        System.out.println("Enter The Data For Matrix :");

         

        for (int i = 0; i < rows; i++)

        {

            for (int j = 0; j < cols; j++)

            {

                matrix[i][j] = sc.nextInt();

            }

        }

         

        System.out.println("Transpose of Matrix is :");

         

        for (int i = 0; i < rows; i++)

        {

            for (int j = 0; j < cols; j++)

            {

                transpose[j][i] = matrix[i][j]; // Just need to change position of i and j

            }

        }

         

        for (int i = 0; i < cols; i++)

        {

            for (int j = 0; j < rows; j++)

            {

                System.out.print(transpose[i][j]+"\t");

            }

             

            System.out.println();

        }

********************************************************************************
//To Reverse And Add A Number Until You Get A Palindrome (number whose reverse ==  original number  . ie 123321 ):