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Re: How to write constructor for an abstarct class?

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On 12/28/2015 7:44 AM, Xue Feng wrote:
> I have written a Shape class to test abstract class. My plan is to
> include two fields x and y to represent the coordinate of a shape, and
> add two constructors to initialize the coordinate. In addition, two
> abstract methods, namely getArea() and getPerimeter(), is included to
> calculate the area and perimeter of a shape respectively. The two
> methods will be overrided by subclass of Shape. The code is as follows:
>
> class Shape {
>      int x, y;
>
>      public Shape(int x, int y) {
>          this.x = x;
>          this.y = y;
>      }
>
>      public Shape() {
>          this(0, 0);
>      }
>
>      public abstract double getArea();
>      public abstract double getPerimeter();
> }
>
> While compiling, the second constructor
>
>      public Shape() {
>          this(0, 0);
>      }
>
> will cause error. I am aware of that Shape is an abstract class, hence
> can not be instantiated. But, how can I write the constructor
> alternately? Thanks.

     I see no problem with the constructor.  What is "error" you get?

     However, the code you posted has a problem: The class itself must be
declared `abstract' if it has abstract methods, as in

	abstract class Shape { ...

     Are you sure that the code you posted is the same code that gives
you trouble?

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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How to write constructor for an abstarct class? Xue Feng <xf.lotus@yahoo.com> - 2015-12-28 20:44 +0800
  Re: How to write constructor for an abstarct class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-28 08:21 -0500
    Re: How to write constructor for an abstarct class? Jan Burse <janburse@fastmail.fm> - 2015-12-28 19:20 +0100
      Re: How to write constructor for an abstarct class? Jan Burse <janburse@fastmail.fm> - 2015-12-28 19:25 +0100
        Re: How to write constructor for an abstarct class? Jan Burse <janburse@fastmail.fm> - 2015-12-28 19:28 +0100
          Re: How to write constructor for an abstarct class? Lew <lewbloch@gmail.com> - 2015-12-28 10:40 -0800
          Re: How to write constructor for an abstarct class? Eric Douglas <e.d.programmer@gmail.com> - 2015-12-28 10:42 -0800
            Re: How to write constructor for an abstarct class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-28 14:29 -0500
            Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-28 22:26 +0100
              Re: How to write constructor for an abstarct class? Eric Douglas <e.d.programmer@gmail.com> - 2015-12-28 13:37 -0800
              Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-28 22:47 +0100
                Re: How to write constructor for an abstarct class? Eric Douglas <e.d.programmer@gmail.com> - 2015-12-28 13:58 -0800
                Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-28 23:06 +0100
                Re: How to write constructor for an abstarct class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-12-28 17:43 -0500
                Re: How to write constructor for an abstarct class? Lew <lewbloch@gmail.com> - 2015-12-28 15:14 -0800
                Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-29 15:02 +0100
                Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:37 -0500
                Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:28 -0500
            Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:21 -0500
              Re: How to write constructor for an abstarct class? Arne Vajhøj <arne@vajhoej.dk> - 2015-12-29 15:22 -0500
  Re: How to write constructor for an abstarct class? j4n bur53 <janburse@fastmail.fm> - 2015-12-29 16:24 +0100

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