Question

I need help with a java error

Question:

Consider a graphics system that has classes for various figures—say, rectangles, boxes, triangles, circles, and so on. For example, a rectangle might have data members’ height, width, and center point, while a box and circle might have only a center point and an edge length or radius, respectively. In a well-designed system, these would be derived from a common class, Figure. You are to implement such a system.

The class Figure is the base class. You should add only Rectangle and Triangle classes derived from Figure. Each class has stubs for methods erase and draw. Each of these methods outputs a message telling the name of the class and what method has been called. Because these are just stubs, they do nothing more than output this message. The method center calls the erase and draw methods to erase and redraw the figure at the center. Because you have only stubs for erase and draw, center will not do any “centering” but will call the methods erase and draw, which will allow you to see which versions of draw and center it calls. Also, add an output message in the method center that announces that center is being called. The methods should take no arguments. Also, define a demonstration program for your classes.

Code:

.

Figure.java

import java.util.Scanner;

public abstract class Figure
{
   public abstract void erase();

   public abstract void draw();
  
   public abstract void center();
}

Rectangle.java

import java.util.Scanner;

public class Rectangle extends Figure
{
   int length;
   int width;

   public Rectangle()
   {
       length=0;
       width=0;
   }

   public Rectangle(int l, int w)
   {
       length=l;
       width=w;
   }

   public void setL(int l)
   {
       length=l;
   }

   public void setW(int w)
   {
       width=w;
   }

   public int getL()
   {
       return length;
   }

   public int getW()
   {
       return width;
   }

   public void erase()
   {
       for(int i=1; i<=length; i++)
       {
           System.out.println();
       }
   }

   public void draw()
   {
       for(int i=1; i<=length; i++)
       {
           if(i==1||i=length)
           {
               for(int j=1; j<=width; j++)
                   System.out.print("a");
           }

           else
           {
               System.out.print("b");
               for(int j=1; j<=2*width-3; j++)
                   System.out.print("c");
               System.out.print("d");
           }

           System.out.println();
       }

   }

   public void center()
   {
       System.out.println("The center is being called.");
       erase();
       draw();
   }

}

Triangle.java

import java.util.Scanner;

public class Triangle extends Figure
{
   private int side;

   public Triangle()
   {
       side=0;
   }

   public Triangle(int s)
   {
       side=s;
   }

   public void setS(int s)
   {
       side=s;
   }

   public int getS()
   {
       return side;
   }

   public void erase()
   {
       for(int i=1; i<=side; i++)
       {
           System.out.println();
       }

   }

   public void draw()
   {
       int oSpace=side-1;//outer spaces
       int iSpace=1;//inner spaces

       for (int i=1; i<=side; i++)
       {
           if(i==1)
           {
               for(int j=1; j<=oSpace; j++)
                   System.out.print("a");
               System.out.print("b");

               for(int j=1; j<=iSpace; j++)
                   System.out.print("c");
               System.out.print("d");
               iSpace+=2;
           }

           oSpace--;
           System.out.println();
       }

   }

   public void center()
   {
       System.out.println("The center is being called.");
       erase();
       draw();
   }
  
}

ShapeDemo.java

import java.util.Scanner;

public class ShapeDemo
{
   public static void main(String args[])
   {
       Scanner input=new Scanner(System.in);

       int l;
       int w;
       int s;

       System.out.println("What is the length of the rectangle?");
       l=input.nextInt();

       System.out.println("What is the width of the rectangle?");
       w=input.nextInt();

       System.out.println("What is the length of the sides for the triangle?");
       s=input.nextInt();

       Figure r=new Rectangle(l,w);

       Figure t=new Triangle(s);

       System.out.println("\nThis is your rectangle:\n");
       r.draw();

       System.out.println("\nThis is your rectangles center:\n");
       r.center();

       System.out.println("\nYour rectangle has been erased.\n");
       r.erase();

       System.out.println("\nThis is your triangle:\n");
       t.draw();

       System.out.println("\nThis is your triangles center:\n");
       t.center();

       System.out.println("\nYour triangle has been erased.\n");
       t.erase();
   }

}

Error:

Rectangle.java:52: error: bad operand types for binary operator '||'
if(i==1 || i=length)
^
first type: boolean
second type: int
1 error

Answer 1

Helping with the error part as requested. I am not sure if the original program will work as expected because I didn't wrote that and it is already supplied in the question.

Error

Rectangle.java:52: error: bad operand types for binary operator '||'
if(i==1 || i=length)
^
first type: boolean
second type: int
1 error

Root Cause:

in if condition we do compare the values, not assign it. i=length means the value of length would be assigned to i but ideally since this is an if condition, we should compare the value of i with length which is done using == operator

Fix

Just replace if(i==1 || i=length) line number 52 in Rectangle.java with

if(i==1 || i==length)

and it would be resolved.