How has Strings and string pool changed in recent Java versions?

In recent Java versions, specifically Java 9 and onward, the handling of strings and the string pool has seen important changes that improve performance and memory efficiency. One of the key changes in Java 9 is the introduction of a compact string representation. This allows the Java Virtual Machine (JVM) to use a byte array to represent strings, which optimizes the memory footprint by using one byte for characters in the ASCII range and two bytes for characters outside that range.

Additionally, the string pool itself hasn't changed fundamentally, but the way strings are stored and retrieved has been enhanced to reduce memory overhead and improve performance during operations such as string concatenation. The use of StringBuilder or StringBuffer is still recommended for mutable string operations to avoid creating excessive immutable string instances.

Overall, these changes signify Java's continuous effort to enhance the efficiency and performance of its string manipulation functionalities.