Hi Friends,
In this post, I'm going to share String interview questions that have been asked in multiple interviews.
Question 1:
How to print duplicate characters from String?
Answer 1:
Steps:
Question 6:
Find duplicate characters in String.
Answer 6:
Question 8:
Count occurrence of given character in String.
Answer 8:
Question 10:
Check if a String is Palindrome.
Answer 10:
A string is palindrome, if reading it from both ends results in same string.
In this post, I'm going to share String interview questions that have been asked in multiple interviews.
Question 1:
How to print duplicate characters from String?
Answer 1:
Steps:
- Run for loop on each character and add that character in HashSet.
- If add() method returns false, just print that character[duplicate one].
Question 2:
Check if two strings are anagrams of each other?
Answer 2:
Two strings are anagrams of each other, if they contain same exact characters.
e.g.: army and mary are anagrams of each other. But Army and Mary are not.
Remember: String.contains(charsequence) checks for capitalization. So, if String is "Abc", then "Abc".contain("a") returns false.
Steps:
- Compare lengths of both strings. If they are different, strings are not anagrams of each other.
- Run for loop on 1st string and check for every character that whether it is present in another string.
- And then create a new string from 2nd string by removing matched character.
Question 3:
Write the code to reverse a string using recursion.
Answer 3:
String sz = "abc";
int index = 0;
StringBuffer strBuffer = new StringBuffer();
public void main(String[] args){
String strReversed = reverse(sz);
System.out.println("Reversed String is : "+strReversed);
}
public String reverse(String str){
index++;
strBuffer.append(str.charAt(str.length()-index));
if(index != str.length())
reverse(str);
return strBuffer.toString();
}
Question 4:
How will you check if a String contains only digits?
Answer 4:
Use Pattern class.
Pattern pattern = Pattern.compile(".*\\d.*");
boolean matched = pattern.matcher(inputString).matches(); // If it returns true, that means, String contains digits only.
Note: If we take Pattern pattern = Pattern.compile(".*\\D.*");, then matches() method will return false, if String contains all digits.
Question 5:
Find all permutations of a string.
Answer 5:
public class StringPermutations{
public static void main(String[] args){
String sz = "ABC";
int length = sz.length();
StringPermutation perm = new StringPermutation();
perm.permute(sz, 0, length-1);
}
private void permute(String sz, int len, int right){
if(len == right)
System.out.println(sz);
else{
for(int i = 1; i<=right; i++){
sz = swap(sz, len, i);
permute(sz, len+1, right);
sz = swap(sz, len, i);
}
}
}
public String swap(String s, int i, int j){
char temp1;
char[] chArray = s.toCharArray();
temp1 = chArray[i];
chArray[i] = chArray[j];
chArray[j] = temp1;
return String.valueOf(chArray);
}
}
Find duplicate characters in String.
Answer 6:
- Convert String to char array using String.toCharArray().
- Put each character in HashSet. If add() method returns false, means, it is a duplicate character and print it.
Question 7:
Count number of vowels and consonants in String.
Answer 7:
- Convert String to char array using String.toCharArray().
- Run a for loop and compare each character with 'a', 'e', 'i' , 'o', 'u'. If character matches with anyone of these, it is a vowel else it is a consonant.
Count occurrence of given character in String.
Answer 8:
- Convert String to char array using String.toCharArray().
- Run for loop and before storing character in HashMap, first call get(char) and check the return value.
- If it is -1, then store character with value 1. Else store it with value++.
Question 9:
How to reverse words in a sentence?
Answer 9:
Sentence: "Javafreeway.blogspot.com" is good tutorial.
Output: "tutorial good is "Javafreeway.blogspot.com"
Steps:
- Use split() method to get a String array of all words.
- Now just iterate this array in reverse order and append words in StringBuffer.
Check if a String is Palindrome.
Answer 10:
A string is palindrome, if reading it from both ends results in same string.
- Convert a String into char array using String.toCharArray().
- Run a for loop in reverse order and store each character in StringBuilder or StringBuffer.
- Now compare original String with this new one. If both are equal , then String is palindrome.
