Top 25 Java String Programming Interview Questions and Answers
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Q1 How to reverse a string in Java? (with or without using built-in functions)
This question is perfect for entry-level Java developers. You can find the . I have also shared how to .
Q2 Write a Java program to find the first non-repeated character in the string?
I have already shared the easiest way to .
Q3 Write a Java program to count the number of words in a given string?
There are many ways to count the number of words in a given string. The simplest of them is given below:
public class CountNumberOfWords { public static void main(String args[]) { String input = "Alive is Awesome"; String[] words = input.trim().split(" "); System.out.println(words.length); } }
Q4 Write a Java program to count the number of occurrences of a given character in a given string?
The most common way of counting the number of occurrences of a given character in a given string is by using for loop. But in the below example, we are counting the number of occurrences of a given character in a given string without using for loop.
public class CountOccurrencesCharacter { public static void main(String args[]) { String input = "Alive is Awesome"; char ch = 'i'; int count = input.length() - input.replaceAll("i", "").length(); System.out.println(count); } }
Q5 Write a Java program to find the duplicate characters in a string?
This question can easily be solved using the HashSet class as shown below in the example. The interviewer may ask to solve this question without using Set/HashSet, so, be prepared for that also.
import java.util.HashSet; import java.util.Set; public class DuplicateCharacters { public static void main(String args[]) { String input = "Alive is Awesome"; HashSet<Character> set = new HashSet<>(); Set<Character> result = new HashSet<>(); for(char ch : input.toCharArray()) { if(!set.add(ch)) result.add(ch); } System.out.println(result); } }
Q6 Write a Java program to count the number of occurrences of each character in a given string?
I have already shared the answer to this question in a separate post on .
Q7 Write a Java program to remove all whitespaces from a given string.
There are two ways to . One is using built-in Java methods. Another way is without using built-in methods. You can prepare for both ways.
Q8 Write a Java program to check if one given string is an anagram of another given string.
I have shared in a separate post to .
Q9 Write a Java program to check if one given string is the rotation of another given string?
I have already shared the code with examples to check if .
Q10 Write a Java program to find the count of characters that are not repeated in the string?
I have already shared the 3 ways to .
Q11 Write a Java program to print the last unique character of the string.
This question is quite similar to Q2, here, we are looking to write a .
Q12 Write a Java program to count the number of digits in a given string?
I have shared .
Q13 Check if a given string is an isogram or not.
This question is mainly asked to entry-level Java developers. I have already shared .
Q14 Write a Java program to get the first character of the string in Java
This question is mostly asked to entry-level Java developers. You can find the Java program to get the first character of the string in Java .
Q15 Write a Java program to shuffle a string in Java.
There are .
Q16 Write a Java program to count the number of commas in a string?
I have already shared .
Q17 Write a Java program to capitalize the first letter of a string in Java.
I have already shared the .
Q18 Write a Java program to find duplicate words in a string?
I shared 3 ways to .
Q19 Write a Java program to check if a string is a Pangram.
I already shared the .
Q20 Write a Java program to remove the first and last characters from the string.
You can find the .
Q21 Write a Java program to check if a string contains special characters.
I shared the .
Q22 Write a Java program to find all substrings of a string in Java.
You can find the solution of the .
Q23 Check if a string is an anagram in Java.
You can find the answer .
Q24 Write a Java program to determine if a string has all unique characters.
You can find the Java program to .
Q25 Write a Java program to find the permutation and combination of a given string.
This is one of the most important questions and should be on your to-do list before appearing for the interview. .
That's all for today. Please mention in the comments if you face any other string programming question in your interview which is not present in the above list.