Primitive Type Wrappers

Primitive Type Wrappers:

Java is primarily an object-oriented language, but for performance and convenience, it includes primitive data types (e.g., int, char, boolean).

• Java provides wrapper classes in the java.lang package for each of the 8 primitive data types, which allows primitives to be treated like objects.

Why Use Wrapper Classes?

• To allow primitive values to be treated as objects (e.g., storing them in collections like ArrayList which can only hold objects).
• To provide useful methods for parsing and converting data.
• Unlike primitives, wrapper classes can hold null, representing no value.
• Java automatically converts primitives to objects and vice versa for convenience.
• They’re commonly used in collections, serialization, reflection, and generics.
• Wrapper classes are immutable — once created, their value can’t be changed.

Primitive Types and Their Wrapper Classes:

Autoboxing and Unboxing: Java automatically converts between primitive types and their corresponding wrapper objects.

• Autoboxing: Converting a primitive to a wrapper object automatically. (e.g., int i = 10; Integer obj = i;)
• Unboxing: Converting a wrapper object to a primitive automatically. (e.g., Integer obj = 20; int j = obj;)

Example:

public class BoxingUnboxingDemo {
    public static void main(String[] args) {
        // Primitive int
        int a = 10;

        // Boxing: converting int to Integer
        Integer obj = Integer.valueOf(a); // Explicit boxing
        System.out.println("Boxed Integer object: " + obj);

        // Unboxing: converting Integer back to int
        int b = obj.intValue(); // Explicit unboxing
        System.out.println("Unboxed int value: " + b);

        // Autoboxing: automatic conversion from int to Integer
        Integer autoBoxed = a;
        System.out.println("Auto-boxed Integer: " + autoBoxed);

        // Auto-unboxing: automatic conversion from Integer to int
        int autoUnboxed = obj;
        System.out.println("Auto-unboxed int: " + autoUnboxed);
    }
}