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Thread: .toString method question!

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    Member Scorks's Avatar
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    Default .toString method question!

    Hello there!

    So, I just finished a rather long program, dealing with inheritance. in each class, I was asked to include a toString method. Now, the problem is, inside of my subclasses I have methods such as getArea and getPerimeter. in my toString method for this class, I want toString to run and print the area of the object that toString is invoked upon, for example. I just don't know the syntax of this... I though it would be:

    "Area : " + this.getArea()

    but it gives me an error. So, how would I refer to this *unknown* object in my toString class?

    Thanks a lot!


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    Default Re: .toString method question!

    What is the error message? Please copy/paste it here in its entirety.

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    Default Re: .toString method question!

    Well, I've chopped that part out. Now, I'm having a lot of trouble with my return statements. NONE of my return statements are printing. It's compiling, but when I run a method on an object, I just get a blank...

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    Default Re: .toString method question!

    We can't read your mind or see what is on your computer screen. You have to post enough information here for us to be able to help you. What code you you have so far, what is it doing (exactly), and what are you expecting (exactly)?

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    Default Re: .toString method question!

    Sorry, here's the code I'm working with:

    class ARectangle extends AnObject {
     
    double Width;
    double Length;
     
    //No parameter constructor
     
    public ARectangle() {
    double Width;
    double Length;
    }
     
    // 2 Parameter constructor
     
    public ARectangle(double Width1, double Length2) {
    Width = Width1;
    Length = Length2;
    }
     
    // 4 Parameter constructor
     
    public ARectangle(double Width1, double Length1, String Colour1, String Filled1) {
    Width = Width1;
    Length = Length1;
    Colour = Colour1;
    Filled = Filled1;
    }
     
    //ACCESSOR AND MUTATOR METHODS
     
    public double geWidth() {
    return Width;
    }
     
    public double getLength() {
    return Length;
    }
     
    public void setWidth(double Width1) {
    Width = Width1;
    }
     
    public void setLength(double Length1) {
    Length = Length1;
    }
     
    //GET AREA METHOD
     
    public double getArea() {
    double Area = (Width*Length);
    return Area;
    }
     
    // GET PERIMETER METHOD
     
    public double getPerimeter() {
    double Perimeter = (Width + Width + Length + Length);
    return Perimeter;
    }
     
    // TOSTRING METHOD
    public String toString() {
    return "\n" + "Width : " + Width + "\n" + "Length : " + Length;
    }

    Then, when I put this in the main method:

    ARectangle rec = new ARectangle(1.0,3.0);
    rec.getArea();

    it compiles, but then I run it and nothing is printed...

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    Default Re: .toString method question!

    The purpose of a toString() method is to provide the desired String representation of an instance of the class in which the toString() method exists for use in an output statement. So, if your main() method (or whatever you're using to test the ARectangle class) included an output statement, like:

    System.out.println( "This is the rectangle: " + rec );

    'rec' would automatically be output as rec.toString(). If you've done that and are getting nothing "printed," then post the full driver program or main method so that we can see what's going on.

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    Default Re: .toString method question!

    ARectangle rec = new ARectangle(1.0,3.0);
    rec.getArea();

    Won't print out anything. Your getArea() method returns a double to the main but since you are not displaying it or assigning it to anything so the main doesn't really do anything with it.

    As for the toString() as mentioned by GregBrannon it is a way for the object to be displayed in the format you want it. If you don't include the toString() method and just use System.out.println(rec); it will give you something like ARectangle@be230d5.

    In your initial post you mentioned doing "Area" + this.getArea(); What error did you get back then? Also keep in mind a toString() method must return a string.

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