A String in Java that is specified as immutable, as the content shared storage in a single pool to minimize creating a copy of the same value. String class and all wrapper classes in Java that include Boolean, Character, Byte, Short, Integer, Long, Float, and Double are immutable.
The key benefits of keeping this class as immutable are caching, security, synchronization, and performance.
String Pool
Java String Pool is the special memory region where Strings are stored by the JVM. Since Strings are immutable in Java, the JVM optimizes the amount of memory allocated for them by storing only one copy of each literal String in the pool.
Security
The String is widely used in Java applications to store sensitive pieces of information like usernames, passwords, connection URLs, network connections, etc. Hence securing String class is crucial regarding the security of the whole application in general
Synchronization
Being immutable automatically makes the String thread safe since they won’t be changed when accessed from multiple threads.
Hashcode Caching
String objects are also widely used in hash implementations like HashMap, HashTable, HashSet, etc. The immutability guarantees Strings that their value won’t change.
Performance
String pool exists because Strings are immutable. In turn, it enhances the performance by saving heap memory and faster access of hash implementations when operated with Strings.
