Does this Java code involving a Book class use proper encapsulation? I feel it can be a lot simpler if I omit some methods but we're required to every method that is in there [especially setters and getters].
Here's the first class:
public class Book
{
private String title;
private double price;
private final double SALES_TAX=0.075;
public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title=title;
}
public double getPrice()
{
return price;
}
public void setPrice(double price)
{
this.price=price;
}
public double getSalesTax()
{
return SALES_TAX;
}
public double increasePrice(double incresePrice)
{
return incresePrice;
}
public double calculateSales(double sales)
{
return sales;
}
}
And the second class:
public class BookDriver
{
public static void main(String[] args)
{
Scanner keyboard=new Scanner(System.in);
Book bookOne=new Book();
Book bookTwo=new Book();
bookOne.setTitle("Life of Pi");
System.out.print("Enter number to buy of "+bookOne.getTitle()+": ");
bookOne.setPrice(13.50*bookOne.calculateSales(keyboard.nextDouble()));
bookOne.setPrice((bookOne.getPrice()*bookOne.getSalesTax())+bookOne.getPrice());
System.out.print("Cost for "+bookOne.getTitle()+" $");
System.out.printf("%.2f"+"\n",bookOne.getPrice());
bookTwo.setTitle("Harry Potter: The Goblet Of Fire");
System.out.print("Enter number to buy of "+bookTwo.getTitle()+": ");
bookTwo.setPrice(22.00*bookTwo.calculateSales(keyboard.nextDouble()));
bookTwo.setPrice((bookTwo.getPrice()*bookTwo.getSalesTax())+bookTwo.getPrice());
System.out.print("Cost for "+bookTwo.getTitle()+" $");
System.out.printf("%.2f"+"\n",bookTwo.getPrice());
System.out.print("Enter percent increase of "+bookOne.getTitle()+": ");
bookOne.setPrice((bookOne.getPrice()*bookOne.increasePrice(keyboard.nextDouble()))+bookOne.getPrice());
System.out.printf("Cost of "+bookOne.getTitle()+": $"+"%.2f"+"\n",bookOne.getPrice());
System.out.print("Enter percent increase of "+bookTwo.getTitle()+": ");
bookTwo.setPrice((bookTwo.getPrice()*bookTwo.increasePrice(keyboard.nextDouble()))+bookTwo.getPrice());
System.out.printf("Cost of "+bookTwo.getTitle()+": $"+"%.2f"+"\n",bookTwo.getPrice());
keyboard.close();
}
}
I know that this is a lot so I'm not really expecting much in terms of a response but anything would help. Thanks!!
Let's look at the point of encapsulation. You have a Class which consists of properties and methods. The idea behind encapsulation is, you want the methods in your class to be the only way to change the value (state) of the properties. Think of it like this: if some other code in the program wants to change the value of one of the properties, it cannot do it itself, it must ask a method on the class they reside in to do it. That way, you control access to the properties.
The way this is implemented is with getter and setter methods of which you have created a few. A getter method returns the value of the property and a setter method changes it to a new value.
1.
Your getter and setter methods up to increasePrice() are good. You are preventing access to the properties other than from the methods on your class.
2.
increasePrice() only spits out what was passed into it. It doesn't change the value of any of the properties and thus has no purpose. If you want to be able to increase the price you can change the method like so:
public void increasePrice(double amountOfPriceIncrease) {
price += amountOfPriceIncrease;
/*
price += amountOfPriceIncrease is the same as
price = price + amountOfPriceIncrease
*/
}
3. This line is a bit troubling. For starters, increasePrice() doesn't do anything other than spit out what was put into it and secondly, there is a lot going on in the one line that makes it complicated and hard to follow.
bookTwo.setPrice((bookTwo.getPrice()*bookTwo.increasePrice(keyboard.nextDouble()))+bookTwo.getPrice());