Thread: Someone help me understand construstors?

Originally Posted by dowd

My first question is can someone explain constructors to me?

In few words: a constructor is a special member of a class that serves to construct and initialize the state of a newly created object.
Every class has always at least 1 constructor. If the programmer doesn't define at least 1 constructor, the compiler puts in a "default" constructor.

Originally Posted by dowd

Ok so I think I get waht your saying could you give me an example?

How and why would I use it?

public class Book {
    private String title;
 
    public Book(String title) {     // constructor
        this.title = title;
    }
}

This Book class has only 1 explicit constructor. It receives a book title and initializes the title field.

So, for example:

Book b1 = new Book("Java I/O, 2nd Edition");
Book b2 = new Book("Effective Java, 2nd Edition");

Each book object has its own title field initialized with the specified title string.

Originally Posted by dowd

ok in a essenses a constructors allows you initalise a variable with different values?

I am getting this right?

Yes, in general a constructor serves at least for 2 things: to call, implicitly or explicitly, the "super" constructor (the constructor of a superclass) and eventually (this is up to you, and depending on your class) to initialize the "state" (fields) of objects of your class.