Why is a String object in Java immutable?

A String object in Java is immutable for several reasons:

• Security: Immutability allows strings to be used as keys in collections and in multithreaded environments without the risk of data modification.
• Caching and reuse: The JVM can cache string literals and reuse them, saving memory.
• Simplified implementation: Immutable objects are easier to implement and debug because their state does not change after creation.

Internally, a string stores characters in a char[] array, which is declared as final, and methods that modify the string actually create a new String object rather than changing the existing one.