? Java Wrapper Classes

? Quick Overview

Wrapper classes in Java convert primitive data types into objects. They allow primitives to be used in collections, APIs, and frameworks that require objects instead of raw values.

? Key Concepts

Each primitive type has a corresponding wrapper class
Wrapper classes belong to the java.lang package
They support methods and utilities unavailable to primitives
Used heavily in Collections and Generics

? Syntax / Theory

int → Integer
double → Double
char → Character
boolean → Boolean
Autoboxing converts primitive → object automatically
Unboxing converts object → primitive automatically

? Code Example — Manual Boxing

? View Code Example

// Converting primitive to wrapper object
int a = 10;
Integer obj = Integer.valueOf(a);
System.out.println(obj);

? Code Example — Autoboxing & Unboxing

? View Code Example

// Java automatically handles boxing and unboxing
Integer x = 20;
int y = x;
System.out.println(x + y);

? Live Output / Explanation

The wrapper object stores primitive values as objects. Java internally converts values during autoboxing and unboxing without explicit method calls.

✅ Tips & Best Practices

Use wrapper classes when working with collections
Avoid unnecessary boxing for performance-critical code
Prefer parseXxx() for string conversions

? Try It Yourself

Create wrapper objects for all primitive types
Compare == vs equals() on Integer
Convert String to Integer using wrapper methods