Both StringBuffer and StringBuilder are classes in Java that provide mutable strings, meaning their contents can be changed without creating new objects. However, they differ mainly in their thread safety and performance characteristics.

Key Differences

  1. Thread Safety:
    • StringBuffer is thread-safe. It ensures that operations on the string buffer are synchronized, meaning it can be safely used in multithreaded environments.
    • StringBuilder is not thread-safe. It does not synchronize its methods, which makes it faster in single-threaded applications or when thread safety is not a concern.

    Example:

    StringBuffer sb1 = new StringBuffer("Hello");
StringBuilder sb2 = new StringBuilder("Hello");
  2. Performance:
    • StringBuffer is slower than StringBuilder due to its synchronization overhead. This makes StringBuffer suitable for use in situations where thread safety is essential, but the extra synchronization comes at a performance cost.
    • StringBuilder is faster than StringBuffer because it does not have the overhead of synchronization, making it ideal for single-threaded use cases or when thread safety is not needed.
  3. Usage:
    • StringBuffer is typically used when strings need to be modified in a multithreaded environment.
    • StringBuilder is preferred for single-threaded applications where performance is a priority.

When to Use

  • Use StringBuffer when:
    • You need thread safety while modifying the string (e.g., in a multi-threaded environment).
  • Use StringBuilder when:
    • You don’t require thread safety, and you want better performance, which is common in single-threaded scenarios.

Example

StringBuffer buffer = new StringBuffer("Thread-safe");
buffer.append(" and mutable");

StringBuilder builder = new StringBuilder("Fast and mutable");
builder.append(" but not thread-safe");

Summary

  • StringBuffer: Thread-safe but slower due to synchronization.
  • StringBuilder: Faster, but not thread-safe, making it ideal for non-concurrent use cases.

In conclusion, the choice between StringBuffer and StringBuilder depends on whether thread safety is a concern and the performance requirements of your application. For single-threaded scenarios, StringBuilder is typically preferred.