/**
 * Linear structures.  Simple collections that provide the primary operations
 * of add() and get().
 *
 * @author Samuel A. Rebelsky
 * @author Yvonne Palm
 */
public interface Linear
{
  /**
   * Add something to the collection.
   */
  public void add(Object thingy);

  /**
   * Get and remove something from the collection.
   * Produces:
   *   thingy, an object.
   * Pre:
   *   The collection is nonempty.
   * Post:
   *   The collection will have one less element.
   *   In particular, it will have one fewer copy of thingy.
   *   No other elements are affected.
   */
  public Object get()
    throws Exception;

  /**
   * Peek at the next thing that get() will return.
   */
  public Object peek()
    throws Exception;

  /**
   * Determine if anything is left in the collection.
   */
  public boolean isEmpty();
} // interface Linear()