/** BagInterface.java
    An interface that describes the operations of a bag of objects.
    @author Frank M. Carrano
    @version 4.0
*/
public interface BagInterface<T>
{
    /**
        Add a new entry to this bag.
        @param newEntry The object to be added as a new entry.
        @return true if the addition is successful, or false if not.
    */
    public boolean add(T newEntry);

    /**
        Retrieve, and place into an array, all entries that are in this bag.
        @return A newly allocated array of all the entries in the bag.
        Note: If the bag is empty, the returned array is empty.
    */
    public T[] toArray();

    /**
        Check whether this bag is empty.
        @return true if the bag is empty, or false if not.
    */
    public boolean isEmpty();

    /**
        Get the current number of entries in this bag.
        @return The integer number of entries currently in the bag.
    */
    public int getCurrentSize();

    /**
        Count the number of times a given entry appears in this bag.
        @param anEntry The entry to be counted.
        @return The number of times anEntry appears in the bag.
    */
    public int getFrequencyOf(T anEntry);

    /**
        Test whether this bag contains a given entry.
        @param anEntry The entry to locate.
        @return true if the bag contains anEntry, or false if not.
    */
    public boolean contains(T anEntry);

    /**
        Remove all entries from this bag.
    */
    public void clear();

    /**
        Remove one unspecified entry from this bag, if possible.
        @return Either the removed entry, if removal was successful, or null.
    */
    public T remove();

    /**
        Remove one occurrence of a given entry from this bag.
        @param anEntry The entry to be removed.
        @return true if the removal was successful, or false if not.
    */
    public boolean remove(T anEntry);
}