String Programming Interview Questions in Java

String Programming Interview Questions

Here we are gonna to discuss some string programming interview questions in java. String handling is the most important topic in core java.

In this article you will see most frequently asked java string programming interview questions and answers.

Let's start java string programs asked in interview one-by-one.

(1) What is the output of following program?

class Test1

{

public static void main(String args[])

{
String a = "javatutorial95"+100+200;

System.out.println(a);

}

}

Output: javatutorial95100200

(2) What is the output of following program?

class Test2

{

public static void main(String args[])

{

String a = 10+20+"javatutorial95"+20+30;

System.out.println(a);

}

}

Output: 30javatutorial952030

(3) Write a program to reverse a String in java without using String API?

class Test3

{

public static void main(String args[])

{
String s = "Best Country";

String reverse = "";

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

{

reverse +=s.charAt(i);

}

System.out.println(reverse);

}

}

Output: yrtnuoC tseB

(4) Write a java program to check String is palindrome or not?

class Test4

{

public static void main(String args[])

{

String name = "MADAM";//String to be checked for palindrom

String reverse = "";

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

{

reverse += name.charAt(i);

}

System.out.println(reverse);

if(reverse.equalsIgnoreCase(name))

{

System.out.println("String is palindrome");

}

else

{

System.out.println("String is not palindrome");

}

}

}

Output: MADAM

             String is plindrome

(5) Write a java program to find the duplicate words and their number of occurrences in a string?

import java.util.*;

class Test5

{

static void duplicateWords(String string1)

{

//splitting string1 into words

String[] words = string1.split(" ");

//creating HashMap with word as key and count as value

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

//checking each words

for(String word : words)

{

if(wordcount.containsKey(word.toLowerCase()))

{
wordcount.put(word.toLowerCase(), wordcount.get(word.toLowerCase())+1);

}

else

{

wordcount.put(word.toLowerCase(), 1);

}

}

Set<String> wordsstring = wordcount.keySet();

for(String word : wordsstring)

{
if(wordcount.get(word)>1)

{

System.out.println(word+"  :  "+wordcount.get(word));

}

}

}

public static void main(String args[])

{
duplicateWords(dog is Dog not cat);

duplicateWords(cat is Dog not cat and cat);

}

}

Output: dog : 2
              cat : 3

(6) Write a java program to count the number of words in a string?

import java.util.*;
class Test6

{

public static void main(String args[])

{

System.out.println("Enter your string");

//using Scanner class

Scanner s = new Scanner(System.in);

String s1 = s.nextLine();

String[] words = s1.trim().split(" ");

System.out.println("Number of word in a string "+words.length);

}

}

(7) Write a java program to count the number of occurrences of each characters in string?

Occurrence of characters in string e.g "javatutorial" j = 1, a = 3, v = 1..

import java.util.*;
class Test7

{

static void characterCount(String string1)

{

HashMap<Character, Integer> hm = new HashMap<Character, Integer>();

//converting given string to char array

char[] ch = string1.toCharArray();

//checking eahc char of ch

for(char c : ch)

{

if(hm.containsKey(c))

{

hm.put(c, hm.get(c)+1);

}

else

{

hm.put(c, 1);

}

}

System.out.println(hm);

}

public static void main(String args[])

{

characterCount("India is a good country");

}

}

(8) How to check total number of vowels in a java string?

There are 5 vowels in a to z alphabet e.g 'a', 'e', 'i', 'o', 'u'.

import java.util.*;

class Test8

{

public static void main(String args[])

{

System.out.println("Enter some string");

Scanner sc = new Scanner(System.in);

String str = sc.nextLine();

char chars[] = str.toCharArray();

int count = 0;

for(char c : chars)

{

switch(c)

{

case 'a':

case 'e':

case 'i':

case 'o':

case 'u':

count++;

break;

}

}
System.out.println("Number of vowels in string "+count);

}

}

Output: Enter some string

              i love you

              Number of vowels in string 5

(9) How to sort the string without using string API in java?

class Test9

{

public static void main(String args[])

{

String original = "zfabcd";

int j = 0;

char temp = 0;

char chars[] = original.toCharArray();

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

{

for(j = 0; j<chars.length; j++)

{

if (chars[j]>chars[i])

{

temp = chars[i];

chars[i]=chars[j];

chars[j]=temp;

}

}

}

for(int k = 0; k<chars.length; k++)

{

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

}

}

}

Output: a
             b
             c
             d
             f
             z

Read More:

Java Array Programming Interview Questions.
Top 10 Java Coding Interview Questions.
Difference Between String and StringBuffer in Java.

Above all the java string programs examples are quite useful in any core java interview.