What characteristics does the String data type have?

The String data type in Java has the following characteristics:

• Immutability: after creating a String object, it cannot be changed. Any operations that seem to modify the string actually create a new object.
• Storage: the string is stored as a character array (char[]), and starting from Java 9, an optimization using byte storage (compact strings) is used.
• String Pool: Java uses a string pool to optimize memory — identical string literals are stored in a single instance.
• Methods: String provides many methods for working with strings — comparison, search, replacement, splitting, etc.

Example:

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

Due to immutability, strings are safe to use in multithreaded environments without additional synchronization.