Tell about the String class in Java. Why is it needed and what is its special feature?

In Java, the String class represents an immutable sequence of characters. This means that once a String object is created, its contents cannot be changed.

Features and purpose:

• Immutability: Any operation that appears to modify a string (for example, concatenation) actually creates a new String object. This ensures safety when working with multithreading and allows strings to be used as keys in collections.

• Optimization through string pool: Java uses a string pool — a special storage for string literals, which helps save memory and speed up string comparison.

• Methods for text manipulation: The class provides many methods for searching, comparing, extracting substrings, changing case, etc.

Example of usage:

String s1 = "hello";
String s2 = s1.toUpperCase(); // creates a new string "HELLO"

System.out.println(s1); // hello
System.out.println(s2); // HELLO

Thus, String is a fundamental and widely used class for working with textual data, providing safety, efficiency, and convenience.