Help with set(index, object) please / new to java

Question

private static void setDobject(Rectangle [] setrect)
          LinkedList<Rectangle> rects = new LinkedList<Rectangle>();
          Rectangle myrectangle = new Rectangle(9.0,9.0);                                                                  
             rects.set(1,myrectangle);
          for(Rectangle x : setrect)
               System.out.print("Rectangle: ");
               System.out.println(x.getLength() + " by " + x.getWidth());
          }  //End of for loop
     }  //End of unsorted
     }  the other previous code works, i have used the add(object) and it works here is the code for that:
private static void addDobject(Rectangle [] addrect)
          LinkedList<Rectangle> rects = new LinkedList<Rectangle>();
          Rectangle myrectangle = new Rectangle(9.0,9.0);                                                                  
             rects.add(myrectangle);
             for(Rectangle x : rects)
               System.out.print("Rectangle: ");
               System.out.println(x.getLength() + " by " + x.getWidth());
          }  //End of for loop
          System.out.println();
     }  //End of unsorted
this is the output error it is giving me :
Part 1 : An Array List of Rectangles
Enter length or 999 to exit: 3
Enter width: 2
Enter length or 999 to exit: 1
Enter width: 2
Enter length or 999 to exit: 10
Enter width: 20
Enter length or 999 to exit: 999
Rectangle: 3.0 by 2.0
Rectangle: 1.0 by 2.0
Rectangle: 10.0 by 20.0
Display Object with added item
Rectangle: 3.0 by 2.0
Rectangle: 1.0 by 2.0
Rectangle: 10.0 by 20.0
Rectangle: 9.0 by 9.0
Displaying Objects with SET item
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 1, Size:
0
at java.util.LinkedList.entry(LinkedList.java:365)
at java.util.LinkedList.set(LinkedList.java:328)
at Lab11.setDobject(Lab11.java:129)
at Lab11.main(Lab11.java:78)
Press any key to continue...
finally here is the Rectangle class i'm using:
public class Rectangle
    private double length;     // Instance variables
    private double width;
    public Rectangle(double l, double w)  // Constructor method
        length = l;
        width = w;
    } // end Rectangle constructor
    public double getLength()             // getter 
         return length;
    } // end getLength
     public double getWidth()             // getter 
         return width;
    } // end getWidth
    public void setLength(double l)      // setter 
         length = l;
    } // end setLength
     public void setWidth(double w)     // setter 
         width = w;
    } // end setWidth
     public double calculateArea()         // calculation method
        return length * width;
    } // end calculateArea
    public void displayRectangle()         // display method
        System.out.println("Rectangle Length = " + length);
        System.out.println("Rectangle Width = " + width);               
    } // end displayRectangle
} // Rectangle ClassHope you can help guys! thanks!

Answer 1

LinkedList<Rectangle> rects = new LinkedList<Rectangle>();rects is an empty LinkedList at this point. It has no elements added to it.
rects.set(1,myrectangle);So you can't set the item at index 1 (the 2nd element in the list) because it doesn't even exist. You need to add items to it.