java - Adding objects to an array from an implemented class -

good morning, apologies if question complex/confusing. in intro java course , having difficulties 1 of assignments! guys on here seem have answer know can help!

this assignment create specifications shapes (rectangles , triangles), must implemeneted such:

all shapes must implement calculated interface calculates area/perimeter. shapemanger class stores calculated shapes in array capable of storing 10 objects...

public class app {     public static void main(string[] args)     {          shapemanager sm      =    new shapemanager();          rectangle       r1  =   new rectangle(100,120,10,13);         sm.addshape(r1);          sm.dump();       } }  public interface calculated {      public double calculatearea();       public double calculateperimeter();       public void dump(); }  public class rectangle implements calculated {     private int xcoord, ycoord, length, width, rectanglearea, rectangleperimeter;     public calculated rectangleshape;      public rectangle(int xcoord, int ycoord, int length, int width)     {         xcoord = xcoord;         ycoord = ycoord;         length = length;         width = width;     }      public double calculatearea()     {         rectanglearea = length * width;         return rectanglearea;     }      public double calculateperimeter()     {         rectangleperimeter = (length *2) + (width * 2);         return rectangleperimeter;     }      public void dump()     {         system.out.println("the area of rectangle = " + rectanglearea);         system.out.println("the perimeter of rectangle =" + rectangleperimeter);     }  }   public class shapemanager {     private calculated[] calcarray;     private calculated rectangle;     public calculated shape;      public shapemanager()     {         calcarray = new calculated[10];     }      public void addshape(calculated s)     {         int address = 0;         while (calcarray[address] != null)         {             address++;         }          calcarray[address] = s;     }      public void dump()     {         (int x = 0; x <= 9; x++)         {              if (calcarray[x] !=null)             {                 calcarray[x].dump();             }         }     }     } 

currently output is:

the area of rectangle = 0 perimeter of rectangle =0

i stuck on doing wrong, , why output isnt calculated properly. assistance on appreciated, thank , patience!

allyso

change dump method to:

public void dump() {     system.out.println("the area of rectangle = " + calculatearea());     system.out.println("the perimeter of rectangle =" + calculateperimeter()); } 

you can improve further removing 2 fields: rectanglearea , rectangleperimeter , make calculate functions this:

public double calculatearea() {       return length * width; } 

now save memory well. rename methods getarea , getperimeter.