String Handling Interview Questions and Answers in Java - 1

Question: 1

What is the difference between String, String Buffer and StringBuilder?


StringBuffer StringBuilder

String is a immutable class

StringBuffer is a mutable class

StringBuilder is a mutable class

New Object is created every time when modified. No new object is created, modification is done in existing one.

No new object is created, modification is done in existing one.

Use String if you require immutability Use StringBuffer in java if you need mutable + thread safety.

Use StringBuilder in java if you require mutable + without  thread safety


Question: 2

Why String is immutable or final in Java?

There are several benefits of String because it’s immutable and final.

String Pool is possible because String is immutable in java.

It increases security because any hacker can’t change its value and it’s used for storing sensitive information such as database username, password etc.

Since String is immutable, it’s safe to use in multi threading and we don’t need any synchronization.

Strings are used in java classloader and immutability provides security that correct class is getting loaded by Classloader.

Question: 3

How to split String in java?

We can use split (String regex) to split the String into String array based on the provided regular expression.

Question: 4

What is String in Java?

String is a Class in java and defined in java.lang package. It’s not a primitive data type like int and long. String class represents characters Strings.

String is used in almost all the Java application and there are some interesting facts that we should know about String.

String is immutable and final in Java and JVM uses String Pool to store all the String Objects.

String is the way we can instantiate a String object using double quotes and overloading of “+” operator for concatenation.

Question: 5

Write a function to find out longest palindrome in a given string?

A String can contains palindrome strings in it and to find longest palindrome in given String is a programming question.

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