Java String Interview Questions and FAQs

Below is a curated list of commonly asked Java String interview questions and FAQs. These questions are useful for freshers as well as experienced developers preparing for technical interviews.

1) How many objects will be created in the following code?

String s1 = "javatpoint";
String s2 = "javatpoint";

2) What is the difference between equals() method and == operator?

3) Is String class final in Java?

4) How to reverse a String in Java?

You can reverse a string using loops, StringBuilder, or recursion. Read more

5) How to check whether a String is Palindrome in Java?

A string is palindrome if it reads the same forward and backward. Read more

6) Write a Java program to capitalize each word in a String

Each word’s first letter is converted to uppercase using logic or String methods. Read more

7) Write a Java program to reverse each word in a String

Each word is reversed individually while maintaining word order. Read more

8) Write a Java program to toggle each word in a String

Uppercase letters are converted to lowercase and vice versa. Read more

9) Write a Java program to reverse and toggle each word in a String

Each word is reversed and character cases are toggled. Read more

10) What is the difference between String and StringBuffer?

String is immutable, while StringBuffer is mutable and thread-safe. Read more

11) What is the difference between StringBuffer and StringBuilder?

StringBuffer is synchronized (thread-safe), whereas StringBuilder is faster but not synchronized. Read more

12) What does the intern() method do in Java?

The intern() method stores the string in the String Constant Pool. Read more

13) How to convert String to int in Java?

You can use Integer.parseInt() to convert a string into an integer. Read more

14) How to convert int to String in Java?

Use String.valueOf() or Integer.toString(). Read more

15) How to convert String to Date in Java?

You can use SimpleDateFormat or DateTimeFormatter. Read more

16) How to optimize Java String creation?

Use string literals, StringBuilder, and avoid unnecessary object creation. Read more

17) How to check whether two Strings are anagrams?

Two strings are anagrams if they contain the same characters in different order. Read more

18) How to find duplicate characters in a String?

Duplicate characters can be found using loops, HashMap, or arrays. Read more

19) Why are Strings immutable in Java?

Immutability improves security, caching, and thread safety. Read more

20) How to remove white spaces from a String?

Use replace() or replaceAll() methods. Read more

21) Java Program to check whether one String is a rotation of another

One string is a rotation of another if it can be obtained by rotating the characters of the original string. Read more

22) Java Program to count the number of words in a String

Words in a string can be counted by splitting the string using spaces or regular expressions. Read more

23) Java Program to reverse a String while preserving the position of spaces

Characters are reversed while spaces remain at their original positions. Read more

24) How to swap two String variables without using a third variable?

Strings can be swapped using concatenation and substring operations. Read more

25) How to remove a particular character from a String?

You can remove a specific character using replace() or replaceAll() methods. Read more

26) How to convert String to Integer and Integer to String in Java?

Use Integer.parseInt() for String to Integer and String.valueOf() for Integer to String conversion. Read more