Create an array of references (initially null) to Washer object instances (say 20 elements).
You then want to populate the array with "random" Washer instances.
Using Math.random() generate values for the inner diameter (id), outer diameter (od), and thickness (thick). Also generate a random value to determine the material (either brass or steel) using some percentage (e.g., 60% brass and 40% steel). Based on these random values construct a new Washer (actually either a BrassWasher or SteelWasher) with the random constructor argument values for id, od, and thick.
This will produce a collection of random type and size washers which are stored in the array.
Pass the array to a method which computes the weight of the collection of washers and report that value.
how would this look like?