3.1 Lesson Outcomes

After completing this lesson, learners will be able to:

• Define Java wrapper classes.
• Convert primitive data types into objects.
• Apply autoboxing and unboxing.
• Parse String values into numeric data types.
• Use wrapper class methods in Java applications.

3.2 Overview

Wrapper classes are object representations of primitive data types in Java. Java provides wrapper classes for all primitive types such as:

• Integer,
• Double,
• Character,
• Boolean,
• and Byte.

Wrapper classes allow primitive values to be treated as objects.

This lesson introduces learners to practical usage of wrapper classes in Java programming.

Wrapper classes are important in:

• collections,
• object-oriented programming,
• data conversion,
• and Java APIs.

Understanding wrapper classes is important because many Java frameworks and collections require objects instead of primitive values.

PA1201 — Identify Wrapper Classes

Each primitive data type has a corresponding wrapper class.

Primitive Type — Wrapper Class

int — Integer
double — Double
char — Character
boolean — Boolean
byte — Byte

Practical Activity

Learners must:

• identify primitive types,
• identify wrapper classes,
• and compare both data representations.

PA1202 — Create Wrapper Class Objects

Wrapper classes can create object representations of primitive values.

Java Example:

Integer number = Integer.valueOf(10);

Double price = Double.valueOf(19.99);

Practical Activity

Learners must:

• create wrapper objects,
• assign values,
• and display wrapper class output.

PA1203 — Apply Autoboxing

Autoboxing automatically converts primitive values into wrapper objects.

Java Example:

Integer number = 20;

Double amount = 99.99;

Practical Activity

Learners must:

• apply autoboxing,
• assign primitive values to wrapper objects,
• and display results.

PA1204 — Apply Unboxing

Unboxing converts wrapper objects back into primitive values.

Java Example:

Integer number = 50;

int value = number;

Practical Activity

Learners must:

• perform unboxing,
• convert objects into primitive values,
• and display output.

PA1205 — Convert Strings to Numbers

Wrapper classes support parsing operations.

Java Example:

String age = “25”;

int num = Integer.parseInt(age);

Practical Activity

Learners must:

• convert Strings into numbers,
• apply parsing methods,
• and display converted values.

PA1206 — Convert Numbers to Strings

Wrapper classes can convert numbers into Strings.

Java Example:

int marks = 80;

String result = String.valueOf(marks);

Practical Activity

Learners must:

• convert numbers into Strings,
• display converted values,
• and compare outputs.

PA1207 — Use Wrapper Class Methods

Wrapper classes provide useful methods.

Wrapper Method — Purpose

parseInt() — Converts String to int
valueOf() — Converts primitive to wrapper object
toString() — Converts value to String

Java Example:

Integer number = Integer.valueOf(100);

System.out.println(number.toString());

Practical Activity

Learners must:

• use wrapper methods,
• apply type conversion,
• and display results.

PA1208 — Create Complete Wrapper Class Program

Wrapper classes are used in practical Java applications.

Java Example:

public class WrapperExample {

public static void main(String[] args) {

Integer age = 25;

Double marks = 89.5;

String text = “100”;

int value = Integer.parseInt(text);

System.out.println(age);

System.out.println(marks);

System.out.println(value);

}

}

Importance of Wrapper Classes

Wrapper classes support:

• object-based programming,
• collections,
• data conversion,
• and flexible Java applications.

3.5 Key Notes / Summary

• Wrapper classes represent primitive data types as objects.
• Java supports autoboxing and unboxing.
• Wrapper classes support parsing and conversion.
• Collections require object data types.
• Wrapper methods simplify type conversion.
• Wrapper classes improve flexibility in Java programming.