Lab Sheet 10: Access Modifiers, Classes, and Objects in Java

Task 1: Understanding Access Modifiers

1. Create a Java class called AccessDemo With the following:

   • One default access variable

   • One public variable

   • One protected variable

   • One private variable

   • Methods to demonstrate access to each variable (some accessible, some not)

2. Create a second class AccessTester in:

   • The same package as AccessDemo

   • A different package from AccessDemo

3. In AccessTester, try to access each variable from AccessDemo and document which accesses work and which don't, explaining why based on their access modifiers.

Task 2: Creating a Simple Class

1. Create a class called BankAccount with:

   • Private instance variables: accountNumber (String), balance (double), accountHolderName (String)

   • Public methods: deposit(), withdraw(), checkBalance()

   • A constructor that initializes the account details

2. Test your class by:

   • Creating two BankAccount objects with different initial values

   • Performing deposit and withdrawal operations

   • Checking balances after each operation

Task 3: Instance vs Class Variables

1. Create a class called Student with:

   • Instance variables: studentID, name, grade

   • A class variable: totalStudents (to keep track of how many Student objects have been created)

   • Appropriate methods to get and set these values

2. Test your class by:

   • Creating 3 Student objects

   • Printing the value of totalStudents after each creation

   • Demonstrating that each object maintains its own instance variables

Task 4: Object References

1. Create a class called Book with:

   • Instance variables: title, author, price

   • Methods to display book information

2. Demonstrate object references by:

   • Creating one Book object

   • Creating two references to the same Book object

   • Modifying the book through one reference and showing the change is visible through the other reference

   • Then creating a new Book object and assigning one reference to it

Task 5: Protected Access Modifier

1. Create a base class Vehicle with:

   • Protected variables: make, model

   • Public method: displayInfo()

2. Create a derived class Car that extends Vehicle with:

   • Additional private variable: numDoors

   • Method to display all information (including inherited protected variables)

3. Test your classes by:

   • Creating a Vehicle object and trying to access its protected members directly

   • Creating a Car object and showing it can access the protected members of Vehicle