What is the purpose of the StringBuilder structure and what task does it solve when working with strings?

StringBuilder in Java is designed for efficient construction and modification of strings. Unlike regular strings (String), which are immutable, StringBuilder allows changing the content without creating new objects.

The task that StringBuilder addresses is optimizing concatenation operations and other string modifications, especially in loops or during multiple changes. Using StringBuilder reduces the load on the garbage collector and improves performance.

Example:

StringBuilder sb = new StringBuilder();
sb.append("Hello");
sb.append(" ");
sb.append("world!");
String result = sb.toString();
System.out.println(result);  // Outputs: Hello world!

If we used regular strings with the + operation, a new object would be created with each concatenation, which is less efficient.