StringBuilder

Description

StringBuilder was introduced in Java 5. It is similar to StringBuffer, but it is not synchronized, which means it is not thread-safe. This lack of synchronization makes StringBuilder generally faster than StringBuffer but not suitable for concurrent use in multithreaded environments.

StringBuilder class in Java are mutable and designed for string manipulation. They provide methods to modify the contents of the string without creating new string objects, which can lead to better performance compared to using regular String objects for string manipulation.

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

Working

Internally it uses a resizable array to store the characters of the string. When we append or modify the contents of the string using methods like append(), insert(), delete(), etc., they directly modify the internal character array of the object without creating new string objects. This allows for efficient string manipulation, especially when dealing with large strings or performing many concatenation operations.

Not Using String Pool

Unlike regular String objects, StringBuilder do not use the string pool for storing string literals. When we create a StringBuilder object and append or modify its contents, new character arrays may be created dynamically to accommodate the changes, but these arrays are not stored in the string pool. This behavior is different from regular String objects, which may use the string pool for storing string literals to optimize memory usage.