Difference between StringBuffer and StringBuilder classes?

Both StringBuffer and StringBuilder are classes in Java that are used to manipulate strings. They are similar in many ways, but there is one key difference between them: their thread safety.

1. StringBuffer:
   • StringBuffer is a thread-safe class, meaning it is designed to be used in multi-threaded environments where multiple threads may access and modify the same StringBuffer object concurrently without conflicts.
   • To achieve thread safety, most methods in StringBuffer are synchronized, which means they are guarded by locks to prevent multiple threads from accessing them simultaneously.
   • Due to the overhead of synchronization, StringBuffer can be slower than StringBuilder in single-threaded environments.

Example usage of StringBuffer:

StringBuffer stringBuffer = new StringBuffer();
stringBuffer.append("Hello ");
stringBuffer.append("World!");

2. StringBuilder:
   • StringBuilder is similar to StringBuffer in functionality but is not thread-safe. It is designed to be used in single-threaded environments or situations where thread safety is not a concern.
   • Unlike StringBuffer, StringBuilder methods are not synchronized, which can make them faster in single-threaded scenarios.
   • If you are working in a single-threaded environment or are sure that your code doesn't require thread safety, StringBuilder is generally preferred for its better performance.

Example usage of StringBuilder:

StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append("Hello ");
stringBuilder.append("World!");

In summary, if you are working in a multi-threaded environment where multiple threads might access and modify the same string concurrently, StringBuffer is the safer choice. If you are in a single-threaded environment or don't need thread safety, StringBuilder is generally more efficient and recommended.