String

Question 1

What is meant by Immutable in the context of Strings?

Answer 1

An immutable object cannot be modified in java. String is an immutable class in java. Once a string is created it cannot be changed.

Question 2

Why a string is considered immutable?

Answer 2

There is a concept of string literal in java. If there are two String variables that reference to a String object “Test”, both these variables reference the same string literal.

Question 3

How many ways are there to create a string?

Answer 3

There are two ways to create a String, one by using String literal and the other by using the “new” operator.

Question 4

Why does java use string literals?

Answer 4

To make java more efficient in memory. If a string already exists in the string constant pool, it can be reused.

Question 5

What is the main difference between a String and StringBuffer object.

Answer 5

String is an immutable object, its value cannot change after creation. StringBuffer is a mutable object. We can keep modifying the contents of a StringBuffer in java.

Question 6

How can you make a class immutable in java?

Answer 6

Mark it as final to prevent it from being extended. Add private modifier to all the fields to prevent direct access. Do not provide setter methods.

Question 7

What is the use of toString() in java?

Answer 7

Object class has a toString() method. This can be used to return the string representation of an object. Java provides default implementation for the toString method, but it can be overridden.

Question 8

Arrange String, stringbuffer and stringbuilder in order of efficiency?

Answer 8

StringBuilder is the most efficient class, then StringBuffer, then String.