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Top 20 Java Programming Interview Questions for SDET

Top 20 Java Programming Interview Questions for SDET

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1. Write a Java program to find the second most frequent character in string “DevLabsAlliance”.

package com.dla;

public class SecondFrequentCharacter {

static final int NO_OF_CHARS = 256;

public static void main(String[] args)

{

  //String to find second frequent character

  String str = "DevLabsAlliance";

  char res = getSecondMostFreq(str);

  if (res != '\0')

  System.out.println("Second most frequent char is " + res);

  else

  System.out.println("No second most frequent character");

}

static char getSecondMostFreq(String str)

{

  //count number of occurences of every character

  int[] count = new int[NO_OF_CHARS];

  int i;

  for (i=0; i< str.length(); i++)

  (count[str.charAt(i)])++;

  // Traverse through the count[] and find second highest element.

  int first = 0, second = 0;

  for (i = 0; i < NO_OF_CHARS; i++)

  {

    /* If current element is smaller than

    first then update both first and second */

    if (count[i] > count[first])

    {

       second = first;

       first = i;

    }

    /* If count[i] is in between first and

    second then update second  */

    else if (count[i] > count[second] &&

    count[i] != count[first])

    second = i;

   }

   return (char)second;

   }

}

// Output
Second most frequent char is L

2. Write a Java program to Reverse a String.

package com.dla;

public class ReverseAString {

     public static void main(String[] args) {

         String s = "DevLabsAlliance";

         String revS = "";

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

             {

                 revS = revS + s.charAt(i);

             }

         System.out.println("The reversed string is "+ revS);

         }

}

// Output
The reversed string is ecnaillAsbaLveD

3. Write a Java program to reverse the order of words in a string.

package com.dla;

import java.util.regex.Pattern;

public class ReverseWordsInString {

     public static void main(String[] args) {

         String str = "Learn Lead And Succeed in DevLabsAlliance";

         Pattern p = Pattern.compile("\\s");

         String[] temp = p.split(str);

         String rev = "";

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

             if (i == temp.length - 1)

             rev = temp[i] + rev;

             else

             rev = " " + temp[i] + rev;

         }

         System.out.println("The reversed string is: " + rev);

     }

}

// Output
The reversed string is: DevLabsAlliance in Succeed And Lead Learn

4. Write a Java program to find the frequency of character in a string.

package com.dla;

public class FrequencyOfCharacter {

     public static void main(String[] args) {

         String str = "DevLabs Alliance is awesome.";

         char ch = 'e';

         int frequency = 0;

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

             if(ch == str.charAt(i)) {

             ++frequency;

         }

     }

     System.out.println("Frequency of " + ch + " = " + frequency);

     }

}

// Output
Frequency of e = 4

5. Write a Java program to sort Strings in Lexicographical(Dictionary) order.

package com.dla;

public class SortStringInDictionaryOrder {

     public static void main(String[] args) {

         String[] words = { "Ruby", "C", "Python", "Java" };

         for(int i = 0; i < 3; ++i) {

         for (int j = i + 1; j < 4; ++j) {

             if (words[i].compareTo(words[j]) > 0) {

                 // swap words[i] with words[j]

                 String temp = words[i];

                 words[i] = words[j];

                 words[j] = temp;

             }

         }

     }

     System.out.println("In lexicographical order:");

     for(int i = 0; i < 4; i++) {

     System.out.println(words[i]);

     }

  }

}

// Output
In lexicographical order:

C

Java

Python

Ruby

6. Write a Java program to replace the SubString with another string.

package com.dla;

public class ReplaceSubStringWithAnotherString {\

     public static void main(String[] args) {

         String str = "Learn, Lead and Succeed in DevLabsAlliance";

         String toBeReplaced = "in";

         String toReplacedWith = "with";

         String[] astr = str.split(toBeReplaced);

         StringBuffer strb = new StringBuffer();

         for ( int i = 0; i <= astr.length-1; i++ ) {

             strb = strb.append( astr[i] );

             if (i != astr.length-1) {

                 strb = strb.append(toReplacedWith);

             }

         }

         System.out.println(strb);

     }

}

// Output
Learn, Lead and Succeed with DevLabsAlliance

7. Write a Java program to find the largest value from the given array.

package com.dla;

public class LargestNumberInArray {

     public static void main(String[] args) {

         int[] arr={28,3,15,9,17,4,23,2};

         int val=arr[0];

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

             if(arr[i] > val){

                 val=arr[i];

             }

         }

         System.out.println("Largest value in the Given Array is "+ val);

     }

}

// Output
Largest value in the Given Array is 28

8. Write a Java program to count the number of words in a string using HashMap.

package com.dla;

import java.util.HashMap;

public class WordCount {

public static void main(String[] args) {

     String str = "Training Training course and certification course in Devlabs Alliance";

     String[] split = str.split(" ");

     HashMap<String, Integer> map = new HashMap<String, Integer>();

     for (int i = 0; i < split.length - 1; i++) {

         if (map.containsKey(split[i])) {

         int count = map.get(split[i]);

         map.put(split[i], count + 1);

     }

     else {

             map.put(split[i], 1);

          }

     }

     System.out.println(map);

     }

}

// Output
{Training=2, in=1, and=1, course=2, Devlabs=1, certification=1}

9. Write a Java program to find whether a string is palindrome or not.

package com.dla;

public class Palindrome {

     public static void main(String[] args) {

     String original = "nitin", reverse = "";

     int length;

     length = original.length();

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

     reverse = reverse + original.charAt(i);

     }

     if (original.equals(reverse))

         System.out.println("The string is palindrome");

     else

         System.out.println("The string is not a palindrome");

     }

}

// Output
The string is palindrome

10. Write a java program to find the duplicate characters in a string.

package com.dla;

public class DuplicateCharacters {

     public static void main(String[] args) {

         String str = new String("DevLabsAlliance");

         int count = 0;

         char[] chars = str.toCharArray();

         System.out.println("Duplicate characters are:");

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

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

                 if (chars[i] == chars[j]) {

                     System.out.println(chars[j]);

                     count++;

                     break;

                 }

             }

         }

     }

}

11. Write a Java program to find the second highest number in an array.

package com.dla;

public class SecondHighestNumberInArray {

     public static void main(String[] args) {

         int arr[] = { 14, 46, 47, 94, 94, 52, 86, 36, 94, 89 };

         int largest = arr[0];

         int secondLargest = arr[0];

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

             if (arr[i] > largest) {

                 secondLargest = largest;

                 largest = arr[i];

             } else if (arr[i] > secondLargest && arr[i] != largest) {

                  secondLargest = arr[i];

             }

         }

         System.out.println("Second largest number in an array is:" + secondLargest);

     }

}

// Output
Second largest number in an array is:89

12. Write a Java Program to create pyramid of numbers with 5 rows

package com.dla;

public class PyramidWith5Rows {

     public static void main(String[] args) {

         int noOfRows = 5;

         // Initializing rowCount with 1

         int rowCount = 1;

         System.out.println("Here Is Your Pyramid");

         // Implementing the logic

         for (int i = noOfRows; i > 0; i--) {

             // Printing i spaces at the beginning of each row

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

                 System.out.print(" ");

             }

             // Printing 'rowCount' value 'rowCount' times at the end of each row

         for (int j = 1; j <= rowCount; j++) {

             System.out.print(rowCount + " ");

         }

         System.out.println();

         // Incrementing the rowCount

         rowCount++;

         }

     }

}

// Output
Here Is Your Pyramid

1

2 2

3 3 3

4 4 4 4

5 5 5 5 5

13. Write a Java program to count occurrences of each character in a string.

package com.dla;

public class EachCharCountInString {

     static final int MAX_CHAR = 256;

     public static void main(String[] args) {

         // Create an array of size 256 i.e. ASCII_SIZE

         int count[] = new int[MAX_CHAR];

         String str = "devlabsalliance";

         int len = str.length();

         // Initialize count array index

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

         count[str.charAt(i)]++;

         // Create an array of given String size

         char ch[] = new char[str.length()];

         for (int i = 0; i < len; i++) {

             ch[i] = str.charAt(i);

             int find = 0;

             for (int j = 0; j <= i; j++) {

                 // If any matches found

                 if (str.charAt(i) == ch[j])

                 find++;

             }

             if (find == 1)

                 System.out.println("Number of Occurrence of " + str.charAt(i) + " is:" + count[str.charAt(i)]);

             }

    }

}

// Output
Number of Occurrence of d is:1

Number of Occurrence of e is:2

Number of Occurrence of v is:1

Number of Occurrence of l is:3

Number of Occurrence of a is:3

Number of Occurrence of b is:1

Number of Occurrence of s is:1

Number of Occurrence of i is:1

Number of Occurrence of n is:1

Number of Occurrence of c is:1

14. Write a Java program to move all zeros to the end of array.

package com.dla;

public class pushZerosToEnd {

     public static void main(String[] args) {

         int arr[] = { 1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0, 9 };

         int n = arr.length;

         int count = 0; // Count of non-zero elements

         // Traverse the array. If element encountered is

         // non-zero, then replace the element at index 'count'

         // with this element

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

         if (arr[i] != 0)

         arr[count++] = arr[i];

         // Now all non-zero elements have been shifted to

         // front and 'count' is set as index of first 0.

         // Make all elements 0 from count to end.

         while (count < n)

         arr[count++] = 0;

         System.out.println("Array after pushing zeros to the end: ");

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

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

     }

}

// Output
Array after pushing zeros to the end:

1 9 8 4 2 7 6 9 0 0 0 0

15. Write a Java program to print Floyd’s triangle with 5 rows.

package com.dla;

public class FloydTriangleWith5Rows {

     public static void main(String args[]) {

         int rows = 5;

         int number = 1;

         for (int i = 1; i <= rows; i++) {

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

                 System.out.print(number + " ");

                 number++;

             }

             System.out.println();

         }

     }

}

// Output

1

2 3

4 5 6

7 8 9 10

11 12 13 14 15

16. Write a Java program to print all prime factors of a given number.

package com.dla;

public class AllPrimeFactors {

     public static void main(String[] args) {

         int n = 315;

         // Print the number of 2s that divide n

         while (n % 2 == 0) {

             System.out.print(2 + " ");

             n /= 2;

         }

         // n must be odd at this point. So we can

         // skip one element (Note i = i +2)

         for (int i = 3; i <= Math.sqrt(n); i += 2) {

             // While i divides n, print i and divide n

             while (n % i == 0) {

                 System.out.print(i + " ");

                 n /= i;

             }

         }

         // This condition is to handle the case when

         // n is a prime number greater than 2

         if (n > 2)

         System.out.print(n);

     }

}

// Output
3 3 5 7

17. Write a Java program to print all prime numbers till 15.

package com.dla;

public class PrimeNumberTill15 {

     public static void main(String args[]) {

             int maxNum = 15;

             // printing primer numbers till the limit ( 1 to 100)

             System.out.println("Printing prime number from 1 to " + maxNum);

             for (int number = 2; number <= maxNum; number++) {

                 // print prime numbers only

                 if (isPrime(number)) {

                 System.out.println(number);

                 }

             }

         }

         /*

         * Prime number is not divisible by any number other than 1 and itself

         *

         * @return true if number is prime
  
         */

         public static boolean isPrime(int number) {

             for (int i = 2; i < number; i++) {

             if (number % i == 0) {

             return false; // number is divisible so its not prime

             }

         }

return true; // number is prime now

     }

}

// Output
Printing prime number from 1 to 15

2

3

5

7

11

13

18. Write a Java program to reverse digits of an integer.

package com.dla;

public class ReverseDigits {

     public static void main(String args[]) {

         int num = 3689;

         int rev_num = 0;

         while (num > 0) {

             rev_num = rev_num * 10 + num % 10;

             num = num / 10;

         }

         System.out.println("Reverse of no. is " + rev_num);

     }

}

// Output
Reverse of no. is 9863

19. Write a Java program to remove duplicates from ArrayList.

package com.dla;

import java.util.*;

public class RemoveDuplicatesFromArrayList {

     public static void main(String[] args) {

         ArrayList<String>

         list = new ArrayList<>(

             Arrays.asList("Dev", "Labs", "Alliance", "Dev", "Labs", "Dev", "DevLabsAlliance"));

             System.out.println("ArrayList with duplicates: " + list);

             // Creating a new ArrayList

             ArrayList<String> newList = new ArrayList<>();

             // Traversing through the first list

             for (String element : list) {

                 // If this element is not present in newList, then add it

                 if (!newList.contains(element)) {

                     newList.add(element);

             }

         }

System.out.println("ArrayList with duplicates removed: " + newList);

     }

}

// Output
ArrayList with duplicates: [Dev, Labs, Alliance, Dev, Labs, Dev, DevLabsAlliance]

ArrayList with duplicates removed: [Dev, Labs, Alliance, DevLabsAlliance]

20. Write a Java program to print all the permutations of a string.

package com.dla;

public class PermutationOfString {

     // Function to print all the permutations of given string

     static void permutation(String s, String result)

         {

             // If string is empty

             if (s.length() == 0) {

                 System.out.print(result + " ");

                 return;

             }

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

                 // ith character of string

                 char ch = s.charAt(i);

                 // Remaining string after excluding the ith character

                 String remainStr = s.substring(0, i) + s.substring(i + 1);

                 // Recursive call

                 permutation(remainStr, result + ch);

             }

         }

    public static void main(String[] args)

     {

         String d = "Dev";

         permutation(d, "");
         
     }
}

// Output
Dev Dve eDv evD vDe veD

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