JavaStrings in Java

StringBuffer vs StringBuilder

Learn the difference between String, StringBuffer, and StringBuilder in Java, including mutability, performance, thread safety, and real-world use cases.

StringBuffer vs StringBuilder in JavaLink to this section

While String objects are immutable, Java provides StringBuffer and StringBuilder classes for mutable strings. These classes allow modification without creating new objects.

Both classes belong to the java.lang package and are widely used in performance-critical applications.

Why StringBuffer and StringBuilder?Link to this section

When frequent string modifications are required, using String can lead to memory overhead. StringBuffer and StringBuilder solve this problem by allowing in-place changes.

tip

Use mutable strings when concatenation happens repeatedly in loops.

StringBufferLink to this section

StringBuffer is thread-safe and synchronized, making it suitable for multi-threaded environments.

note

Thread safety makes StringBuffer slower compared to StringBuilder.

StringBuilder Link to this section

StringBuilder is not thread-safe and is faster than StringBuffer. It is best suited for single-threaded applications.

warning

Avoid using StringBuilder in multi-threaded environments without synchronization.

Key DifferencesLink to this section

Understanding the differences helps you choose the right class.

  1. String → Immutable, thread-safe
  2. StringBuffer → Mutable, thread-safe, slower
  3. StringBuilder → Mutable, not thread-safe, faster

StringBuffer vs StringBuilder
Question 1 of 5

Which class is thread-safe?

StringBuffer vs StringBuilder

medium
  1. Write a program that appends text using String and observe memory behavior.
  2. Rewrite the same program using StringBuilder and compare performance.
  3. Use StringBuffer in a multi-threaded scenario and explain why it is safe.
  4. Convert a String into StringBuilder and modify it.
  5. Explain when to prefer String over StringBuilder in real-world applications.