Creating an Arraylist of Objects

If you want to allow a user to add a bunch of new MyObjects to the list, you can do it with a for loop: Let's say I'm creating an ArrayList of Rectangle objects, and each Rectangle has two parameters- length and width.

//here I will create my ArrayList:

ArrayList <Rectangle> rectangles= new ArrayList <>(3); 

int length;
int width;

for(int index =0; index <3;index++)
{JOptionPane.showMessageDialog(null, "Rectangle " + (index + 1));
 length = JOptionPane.showInputDialog("Enter length");
 width = JOptionPane.showInputDialog("Enter width");

 //Now I will create my Rectangle and add it to my rectangles ArrayList:

 rectangles.add(new Rectangle(length,width));

//This passes the length and width values to the rectangle constructor,
  which will create a new Rectangle and add it to the ArrayList.

}