String vs StringBuilder in Java - Quick Revision & Key Differences

overview

Recall & Review

beginner

What is a String in Java?

A String is an object that holds a sequence of characters. It is immutable, meaning once created, it cannot be changed.

beginner

What does immutable mean for a String?

Immutable means the String's content cannot be changed after it is created. Any modification creates a new String object.

beginner

What is a StringBuilder in Java?

StringBuilder is a class used to create mutable sequences of characters. It allows you to change the content without creating new objects.

intermediate

Why use StringBuilder instead of String for many changes?

Because StringBuilder can change its content without making new objects, it is faster and uses less memory when you do many modifications.

beginner

How do you convert a StringBuilder back to a String?

Use the toString() method of StringBuilder to get a String with the current content.

Which of the following is immutable in Java?

A StringBuffer

B StringBuilder

C String

D StringBuilder and StringBuffer

Which class is best for building a string with many changes efficiently?

A StringBuilder

B String

C Integer

D Character

What method converts a StringBuilder to a String?

A toString()

B toCharArray()

C toStringBuilder()

D toStringBuilderString()

If you add characters to a String, what happens internally?

A The original String changes

B The StringBuilder is updated

C The String becomes mutable

D A new String object is created

Which is true about StringBuilder?

A It is slower than String for many changes

B It is mutable and faster for many changes

C It cannot be converted to String

D It is immutable

Explain the difference between String and StringBuilder in Java.

When should you choose StringBuilder over String?