A String in Java is an object of the String class used to represent a sequence of characters. Unlike arrays, it has built-in methods for manipulation.

Strings are immutable because:

• They are stored in the String Pool for memory efficiency.
• Immutability ensures security, thread-safety, and caching benefits.

• == → Compares references (memory addresses).
• .equals() → Compares values (actual content of the String).

• String → Immutable.
• StringBuilder → Mutable, faster, not thread-safe.
• StringBuffer → Mutable, thread-safe, slightly slower due to synchronization.

The String Pool (or String Intern Pool) is a special area in the heap memory where Java stores string literals.

• If a string with the same value already exists in the pool, the new reference points to the existing object (saves memory).