Can you name data types that cannot be changed after creation?

Java has several data types and classes whose objects are immutable after creation. These include:

• String — once created, its content cannot be changed. Operations that seem to modify a string actually create a new object.
• Primitive wrapper classes (e.g., Integer, Double, Boolean) — objects of these classes are immutable.
• BigInteger and BigDecimal — classes for large numbers and precise arithmetic, whose objects are also immutable.

Example:

String s = "hello";
String s2 = s.toUpperCase(); // s remains unchanged, s2 is a new object

If you need to create your own immutable class, you typically make fields final and do not provide setters.