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Thread: Someone help me understand construstors?

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    Default Someone help me understand construstors?

    Hello All

    I cannot express how happy I am to have found a platform to ask all my Java related questions and there is many.

    first off I am complete beginner in the software development/programming field and have decided to start with Java as it can be used on any system and it seems that Java developers are in huge demand.

    My first question is can someone explain constructors to me?

    I keep re reading the same section of the book and cannot get my head around it? Can someone explain and give me an easy to follow example?


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    Default Re: Someone help me understand construstors?

    Quote Originally Posted by dowd View Post
    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.
    Andrea, www.andbin.net SCJP 5 (91%) SCWCD 5 (94%)

    Useful links for Java beginners My new project Java Examples on Google Code

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    GregBrannon (December 9th, 2013)

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    Default Re: Someone help me understand construstors?

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

    How and why would I use it?

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    Default Re: Someone help me understand construstors?

    Quote Originally Posted by dowd View Post
    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.
    Andrea, www.andbin.net SCJP 5 (91%) SCWCD 5 (94%)

    Useful links for Java beginners My new project Java Examples on Google Code

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    Default Re: Someone help me understand construstors?

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

    public class User {
    private String Name;

    public User(String name) { // constructor
    this.name = name;
    }
    }

    So you would have:

    User User1 = new user (Bob Smiith)
    User User2 = new user (Tom Smith)

    I am getting this right?

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    Default Re: Someone help me understand construstors?

    Welcome to the Forum! Please read this topic to learn how to post your code correctly along with other useful info for newcomers.

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    Default Re: Someone help me understand construstors?

    Quote Originally Posted by dowd View Post
    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.
    Andrea, www.andbin.net SCJP 5 (91%) SCWCD 5 (94%)

    Useful links for Java beginners My new project Java Examples on Google Code

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    dowd (December 9th, 2013)

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    Default Re: Someone help me understand construstors?

    Excellent that kind of makes sense now thanks alot.

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