Thread: how to solve this question ? please help me

Create an abstract class called GeometricFigure. Each figure includes a height, a width, a figure type and an area. Include an abstract method to determine the area of the figure. Create two subclasses called Square and Triangle. Create an application that demonstrates creating objects of both subclasses and store them in an array

can you give the code for this question ? i just need the code

Originally Posted by pejagusta

can you give the code for this question ? i just need the code

Giving the code would not be the right thing to do, read this instead

Originally Posted by pejagusta

can you give the code for this question ? i just need the code

Sure.

abstract class GeometricFigure implements MandatoryBackgroundChecks extends AHelpingHand throws Frisbees
{
     private String WhatToDo = "Do your own homework.";
 
     protected void message()
      {
      System.out.println(WhatToDo);
       }
}

i done for this code but i have many error

Thanks for the update.

And how can we help? We can't see your code or your errors. What are you expecting us to do?

Originally Posted by pejagusta

i done for this code but i have many error

What do you mean? Did my code not work? Or did you write something and you're having trouble with it? If you post your code (remember to use code tags) and we'll see what we can do.

class Triangle {
private int width, height;
public Triangle(int w, int h) {
width = w;
height = h;
}
public void setWidth(int w) {
width = w;
}
public void setHeight(int h) {
height = h;
}
}

class Triangle extends Square {
public Square(int size) {
setWidth(size);
setHeight(size);
}
}

public Square(int size) { (error: invalid method declaration; return type required line 2)

First off, please use code tags for your code.

Secondly, I'm not sure where you're going with this. It looks like you declared the Triangle class twice.

Third, the statement public Square(int size) looks like you're defining a method, but there are 2 problems: 1) it's not inside any sort of class and 2) it doesn't have a return type.

Look at this first block of code you posted:

class Triangle 
{
        private int width, height;
 
        public Triangle(int w, int h) 
                {
                width = w;
                height = h;
                }  //End of constructor method.
 
          public void setWidth(int w)  
                {
                width = w;
                 }  //End of setWidth method
 
           public void setHeight(int h) 
               {
                height = h;
                } //End of setHeight method.
}   //End of class body.

Do you see how each of those three methods is contained completely within the body of the Triangle class? That's kind of where your error message is coming from, because you didn't do that later on. When you write public Square(int size) , you're not inside any sort of class.

The other thing is that you're extending the wrong thing according to the parameters of the assignment. You need to declare a class called GeometricFigure and extend THAT. Define GeometricFigure as abstract by preceding the class declaration with the keyword abstract. So like if you wanted your Triangle class to be abstract, instead of class Triangle you would write abstract class Triangle.

Inside the class body, define variables and methods to match the things that every shape has. Your instructor has even told you exactly what those are: height, width, type, and area. Then use inheritance (the extends keyword) to define two classes called Square and Triangle. DO NOT define height, width, type, and area for those two objects; by extending GeometricFigure, you can use the height, width, type, and area attributes from that class.

Think of it like this.

 
public class abstractionDisplay  //Primary program.
{
 
     public static void main(String[] args)
     {
      Son me = new Son("Steve");
       me.secretFamilyChiliRecipe();
     }
} //End of main.
 
abstract class Dad  //Abstract class
{
    protected String lastName = "Smith";
 
    protected void secretFamilyChiliRecipe()
           {
            System.out.println("Let's whip up some of our famous " +lastName +" family chili!");
           }
}  //End of abstract class.
 
class Son extends Dad  //Concrete class.
{
     private String firstName;
 
      Son(String name)
           {
            this.firstName = name;
            System.out.println("My name is " +this.firstName +" " +this.lastName +" of the " +this.lastName +" family.");
            }
}  // End of concrete Son class.

Notice how the object "me" was of type "Son", yet it accessed a method defined in the class "Dad"? Did you notice how I referenced the "lastName" string for the Son class even though I didn't define one in the Son class? That's what inheritance lets you do; you extend a class and you can access its methods and variables as well as the methods and variables within your own class.

I hope that helps.

(DO NOT define height, width, type, and area for those two objects; by extending GeometricFigure, you can use the height, width, type, and area attributes from that class) what do you mean? can give examples?

Originally Posted by pejagusta

(DO NOT define height, width, type, and area for those two objects; by extending GeometricFigure, you can use the height, width, type, and area attributes from that class) what do you mean? can give examples?

Actually, now that I look at the assignment as given:

Create an abstract class called GeometricFigure. Each figure includes a height, a width, a figure type and an area. Include an abstract method to determine the area of the figure. Create two subclasses called Square and Triangle. Create an application that demonstrates creating objects of both subclasses and store them in an array

I'm a little perplexed myself. Height, width, and area are higher level attributes that you could define in an abstract class and then have a concrete class inherit. Squares and triangles both have those. Figure type, though, that definitely seems like something that would have to be unique to the concrete classes (square and triangle). Unless I'm missing something here.

Do you understand the example I gave earlier? Do you see how I defined a lastName variable and a secretFamilyChiliRecipe() method in the Dad class, then used them in the Son class, but never at any time actually created an instance of the Dad class? I accessed those through the Son class. The abstract class "Dad" was not instantianted and it could not be. That's kinda what you have to do with your project. Create a GeometricFigure class with height, width, and area, plus methods to handle those. Area will have to be computed through a method, but you have some leeway with what you do with height and width. You could declare them as protected and set them directly, or declare them as private and write getter and setter methods for them. Going the route of protected is probably easier.

Still don't get what your instructor wants with that figure type field though.

can u give me the output for my question .

What question?

Create an abstract class called GeometricFigure. Each figure includes a height, a width, a figure type and an area. Include an abstract method to determine the area of the figure. Create two subclasses called Square and Triangle. Create an application that demonstrates creating objects of both subclasses and store them in an array

i want the output .

--- Update ---

what is your question ?

The output depends on the input. If you wrote this, then gave a height and width of 4, you would get an area of 16 for the square and 8 for the triangle.