Most asked Java Interview questions on String
By Uncategorized

Most asked Java Interview questions on String: Java interviews often include questions related to string manipulation and handling, as strings are fundamental data types in Java programming. Candidates are expected to demonstrate their understanding of string operations, methods, and best practices.

Most asked Java Interview questions on String

1. What is a String in Java?

A String in Java is a sequence of characters treated as an object. It is an immutable class, meaning once created, its value cannot be changed. Strings can be instantiated using string literals or the new keyword.

2. How do you create an empty string in Java?

An empty string in Java can be created using either String str = "" or String str = new String().

3. What is the difference between String, StringBuilder, and StringBuffer?

  • String: Immutable, thread-safe, and suitable for immutable strings.
  • StringBuilder: Mutable, not thread-safe, and efficient for string manipulation.
  • StringBuffer: Mutable, thread-safe, and less efficient due to synchronization.

4. How can you concatenate strings in Java?

Strings can be concatenated in Java using the + operator, the concat() method, or the append() method of the StringBuilder or StringBuffer classes.

5. Explain the equals() method in Java strings.

The equals() method in Java strings is used to compare the content of two strings. It returns true if the content of both strings is equal; otherwise, it returns false.

6. How do you compare strings in Java?

Strings in Java can be compared using the equals() method for content comparison and the == operator for reference comparison.

7. Can you convert a string to uppercase or lowercase in Java?

Yes, strings can be converted to uppercase using the toUpperCase() method and to lowercase using the toLowerCase() method in Java.

8. How do you find the length of a string in Java?

The length of a string in Java can be found using the length() method.

9. Explain the charAt() method in Java strings.

The charAt() method returns the character at a specified index within a string. The index starts from 0.

10. What is the substring() method used for in Java strings?

The substring() method is used to extract a substring from a given string based on specified start and end indices.

11. How can you check if a string contains a specific substring in Java?

You can use the contains() method to check if a string contains a specific substring in Java.

12. Explain the split() method in Java strings.

The split() method is used to split a string into an array of substrings based on a specified delimiter.

13. What is the trim() method used for in Java strings?

The trim() method removes leading and trailing whitespace from a string in Java.

14. How can you convert an integer or other data types to a string in Java?

You can use the valueOf() method or concatenation with an empty string to convert other data types to a string in Java.

15. Can you reverse a string in Java? If yes, how?

Yes, a string can be reversed in Java using various methods such as using StringBuilder‘s reverse() method, iterating through the string, or using recursion.

16. Explain the indexOf() and lastIndexOf() methods in Java strings.

The indexOf() method returns the index of the first occurrence of a specified character or substring within a string, while lastIndexOf() returns the index of the last occurrence.

17. How do you convert a string to an array of characters in Java?

You can use the toCharArray() method to convert a string to an array of characters in Java.

18. What is string interning in Java?

String interning is the process of storing only one copy of each distinct string value, which helps conserve memory and allows for efficient string comparison using reference equality.

19. Explain the difference between StringBuffer and StringBuilder classes.

The main difference is that StringBuffer is synchronized and thread-safe, while StringBuilder is not synchronized, making it more efficient in single-threaded scenarios.

20. How do you convert a string to a numeric data type in Java?

You can use methods like parseInt() or parseDouble() to convert a string to an integer or a double, respectively, in Java