Introduction to Objects - Advanced Topics in Java: Core Concepts in Data Structures - page 34

We can do this, but we must first write an appropriate constructor, one defined with two String parameters.
The following shows how it can be done:

public Book(String a, String t) {
author = a;
title = t;
}

Here are some important points to note:

• A constructor for a class has the same name as the class. Our class is called Book ; therefore, the

constructor must be called Book . Since a constructor is meant to be used by other classes, it is
declared public .
A constructor can have zero or more parameters. When called, the constructor must be given

•

the appropriate number and type of arguments. In our example, the constructor is declared
with two String parameters, a and t . When calling the constructor, two String arguments
must be supplied.

• The body of the constructor contains the code that would be executed when the constructor

is called. Our example sets the instance variable author to the first argument and title to the
second argument. In general, we can have statements other than those that set the values of
instance variables. We can, for instance, validate a supplied value before assigning it to a field.
We will see an example of this in the next section.

• A constructor does not have a return type, not even

void .
If initial values are provided for instance variables in their declaration, those values are stored •

before the constructor is called.

For example, suppose the class Book is now declared as follows:

public class Book {
private static double Discount = 0.25;
private static int MinBooks = 5;

private String author = "No Author";
private String title;
private double price;
private int pages;
private char binding = 'P'; // for paperback
private boolean inStock = true;

public Book(String a, String t) {
author = a;
title = t;
}
} //end class Book

The statement

Book b = new Book("Noel Kalicharan", "DigitalMath");