3.1 Lesson Outcomes

After completing this lesson, learners will be able to:

• Define reference types in Java.
• Create objects using reference variables.
• Differentiate between primitive and reference types.
• Assign and use object references.
• Apply reference types in Java programs.

3.2 Overview

Reference types in Java store references (memory addresses) to objects instead of actual values. Classes, arrays, strings, and objects are examples of reference types.

This lesson introduces learners to the practical use of reference types and object references in Java applications.

Reference types are important in:

• object-oriented programming,
• memory management,
• software applications,
• and data structures.

Understanding reference types is important because modern Java applications rely heavily on objects and object references.

PA0701 — Define Reference Types

Reference types store references to objects in memory.

Examples of Reference Types

Primitive vs Reference Types

Practical Activity

Learners must:

• identify reference types,
• compare primitive and reference types,
• and explain object references.

PA0702 — Create Objects Using Reference Variables

Objects are created using the:

Plain text

new

keyword.

Example Object Creation

Java

String name = new String(“Alice”);

Java

Student student = new Student();

Practical Activity

Learners must:

• create objects,
• assign reference variables,
• and display object information.

PA0703 — Assign Reference Variables

Reference variables can point to objects in memory

Example

Java

Student s1 = new Student();

Student s2 = s1;

Explanation

Both variables reference the same object in memory.

Practical Activity

Learners must:

• assign reference variables,
• compare references,
• and observe shared object behavior.

PA0704 — Use null References

Reference variables can contain:

Plain text

null

when they do not reference an object.

Example

Java

Student student = null;

NullPointerException Example

Java

student.display();

Practical Activity

Learners must:

• assign null references,
• identify null reference errors,
• and prevent runtime exceptions.

PA0705 — Compare Reference Variables

Reference variables can be compared using:

Plain text

==

operator.

Example

Java

String a = “Java”;
String b = “Java”;

System.out.println(a == b);

Practical Activity

Learners must:

• compare object references,
• test equality,
• and display comparison results.

PA0706 — Create a Reference Type Program

Reference types are commonly used in object-oriented applications.

Example Program

Java

class Student {

String name;
}

public class ReferenceExample {

public static void main(String[] args) {

Student student = new Student();

student.name = “Alice”;

System.out.println(student.name);
}
}

Importance of Reference Types

Reference types support:

• object-oriented programming,
• dynamic memory usage,
• and reusable software structures.

3.5 Key Notes / Summary

• Reference types store object references in memory.
• Objects are created using the new keyword.
• Strings, arrays, and classes are reference types.
• null means no object reference exists.
• Reference variables can point to the same object.
• Reference types are important in object-oriented programming.