Top 20 Java Programming Interview Questions for SDET
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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Both trainers (Ravi and Naresh) were excellent in their approach. Session was less of a theory and more of a practical. And even the theory part was quite interesting. A bit issue with the volume of information which I had received in just a span of 2-3 days - it seemed a bit over-loaded. But overall, it has given me a great platform to take it forward from here! Varenya Varshney
6/02/2019- Training provided by the trainers here is completely awesome. Trainer is highly qualified in their areas with practical experience. Also amenities provided during training by institute is great Abhishek Tripathi
6/02/2019 - It was good session, I left my training room with basic knowledge on all the tools. Tutors have great knowledge and experience on the tools. But three days is not enough time. sairam shyamala
6/30/2019 - Excellent Training program. Training courses and trainers are very good. Trainer will explain you as many time you ask the question. Best thing is hands on based training. You learn by doing. Looking for more courses from here. Vijay Kumar
6/30/2019 - Training provided by the trainers in DevLabs Alliance is completely awesome. Trainers are highly qualified in their areas with practical experience. Since it is 3 days training we have completely got the opportunity to have hands on. Salaja K
6/30/2019
