PListInterface.java

public interface PListInterface {

  public void add(Object item);
    // adds item to the start of the PList

  public void append(Object item);
    // places item at the end of the PList

  public void concatenate(PListInterface plist);
    // joins plist to this PList to create a longer list

  public void delete(int index);
    // removes the item at index from the PList.
    // if the index does not exist, nothing happens

  public Object get(int index);
    // returns the data item at index

  public void insert(Object item, int index);
    // places item at the specified index
    // if the index is past the end of the list,
    // item is added at the end of the PList

  public int length();
    // returns length of the PListInterface

  public void print();
    // displays to the screen the items in PList from beginning to end
    // this is an option used for testing and verification

  public void remove(Object item);
    // removes the data entry that matches item from the PList

  public void sort();
    // sorts all items in PList by comparing the toString() values
    // of each data item

}