String Interview Questions Java
string interview questions in Java
String Interview Questions Java
String interview questions in Java often focus on the manipulation and comparison of strings, such as determining if two strings are anagrams, finding the longest common prefix among a set of strings, or reversing a string without using built-in functions. Additionally, questions may require knowledge of string immutability, string concatenation efficiency, and the difference between == and equals() when comparing strings in Java. It is important for candidates to have a strong understanding of Java's String class and its various methods to perform well in such interviews.
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1 - What is the difference between String, StringBuilder, and StringBuffer in Java?
String is immutable, meaning its value cannot be changed once it is created. StringBuilder and StringBuffer are mutable and can be modified. StringBuilder is not thread safe, while StringBuffer is thread safe.
2) How can you convert a String to an integer in Java?
You can use the Integer.parseInt() method to convert a String to an integer in Java. This method parses the String argument as a signed decimal integer.
3) Explain the difference between == and equals() method in Java when comparing Strings.
The == operator checks for reference equality, meaning it checks if two variables point to the same memory location. The equals() method checks for value equality, meaning it checks if the actual contents of the Strings are the same.
4) How can you find the length of a String in Java?
You can use the length() method to find the length of a String in Java. This method returns the number of characters in the String.
5) Explain what is meant by String pooling in Java.
String pooling is a technique used by Java to optimize memory usage and improve performance. When a String is created using double quotes, Java checks if a String with the same value already exists in the pool. If it does, the existing String object is returned instead of creating a new one.
6) How can you check if a String is empty or null in Java?
You can use the isEmpty() method to check if a String is empty, and you can use the StringUtils.isEmpty() method from the Apache Commons library to check if a String is null or empty.
7) Can you modify a String in Java?
No, Strings in Java are immutable, meaning their value cannot be changed once they are created. If you need to make modifications to a String, you can use StringBuilder or StringBuffer instead.
8) Explain what is a String Tokenizer in Java.
A StringTokenizer is a class in Java that is used to break a String into tokens (smaller parts). It provides methods to retrieve these tokens one by one. It is useful for parsing and processing text data.
9) How can you concatenate Strings in Java?
You can use the + operator to concatenate Strings in Java. You can also use the concat() method or join() method introduced in Java 8 for concatenating multiple Strings.
10) What is the difference between String and StringBuffer in terms of performance?
String objects are immutable, which means a new String object is created every time you make a modification. StringBuffer, on the other hand, is mutable and allows you to perform multiple operations on the same object without creating new objects, making it more efficient in terms of performance.
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