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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);
}
}
Ouput: 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. What is the difference between SDET and manual Tester?
SDET is a highly skilled resource having both development and testing skills whereas manual testers have limited programming skills and can only prepare and execute the test cases.
SDETs can develop test automation tools and can use it but testers are not expected to develop the automation tools, they can only use the various automation tools.
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