В чем отличие между StringBuilder и StringBuffer?

Property	StringBuilder	StringBuffer
Thread safety	Not thread-safe	Thread-safe
Performance	Higher	Lower
Synchronization	No method synchronization	Methods are synchronized
Usage	In single-threaded environments	In multi-threaded environments

Both classes are designed for modifying character sequences without creating a new string object for each operation. The main difference lies in thread safety and, consequently, in performance.

// Example of using StringBuilder
StringBuilder sb = new StringBuilder("Hello");
 sb.append(" ");
 sb.append("World");
String result = sb.toString(); // result = "Hello World"

// Example of using StringBuffer
StringBuffer sbf = new StringBuffer("Hello");
 sbf.append(" ");
 sbf.append("World");
String result = sbf.toString(); // result = "Hello World"

In a multi-threaded environment, using StringBuffer guarantees correct operation when accessed simultaneously from different threads, whereas StringBuilder may lead to unpredictable results (race conditions). In a single-threaded environment, using StringBuilder is preferable due to better performance, as synchronization overhead is absent.