Learn Fundamentals of Java Programming “Getter and Setter Methods in Java Programming ” Lesson 21

Getter and Setter Methods

Private data members of a class cannot be accessed outside the class however, you can give controlled access to data members outside the class through getter and setter methods. A getter method returns the value of a data member. For example we could define a getter method in the Book class for the price data member as given below:

double getPrice() {
return price;
}

Similarly, we define a setter method but control how the price is set. We do not allow a book price to become lower than 100.0.

void setPrice(double newprice) {

if (newprice < 100)

System.out.println(“Price cannot be set lower than 100!”);
elses
price = newprice;
}

In the BookTest class, the getter and setter methods can be used to retrieve and set a new price for a book (Figure 1.8i). Let’s say the BookTest class wants to discount the price of the book1 object by 20%, we first get the book’s price using the getPrice() method, use the price to determine a discounted price for the book, and then use the setPrice() method to change the price of the book. The code for the same is as below:

double bookprice = book1.getPrice ();
bookprice = – 20*bookprice/100;
book1.setPrice (bookprice);

Now book1’s data member price is set to 360.0 (Figure 1.8j). However if a discount caused a book object’s price to fall below 100, the setter method would not change the price. Without a controlled setter function, the BookTest class could have changed the book’s price arbitrarily.