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package rac; import listFW.*; /** * Defines the interface for a restricted access container. */ public interface IRAContainer { /** * Empty the container. * NOTE: This implies a state change. * This behavior can be achieved by repeatedly removing elements from this IRAContainer. * It is specified here as a convenience to the client. */ public void clear(); /** * Return TRUE if the container is empty; otherwise, return * FALSE. */ public boolean isEmpty(); /** * Return TRUE if the container is full; otherwise, return * FALSE. */ public boolean isFull(); /** * Return an immutable list of all elements in the container. * @param fact for manufacturing an IList. */ public IList elements(IListFactory fact); /** * Remove the next item from the container and return it. * NOTE: This implies a state change. * @throw an Exception if this IRAContainer is empty. */ public Object get(); /** * Add an item to the container. * NOTE: This implies a state change. * @param input the Object to be added to this IRAContainer. * @throw an Exception if this IRAContainer is full. */ public void put(Object input); /** * Return the next element in this IRAContainer withour removing it. * @throw an Exception if this IRAContainer is empty. */ public Object peek(); }
- Restrict the users from seeing inside or working on the inside of the container.
- Have simple put(data) and get() methods. Note the lack of specification of how the data goes in or comes out of the container.
- However, a "policy" must exist that governs how data is added ("put") or removed ("get"). Examples:
- First in/First out (FIFO) ("Queue")
- Last in/First out (LIFO) ("Stack")
- Retrieve by ranking ("Priority Queue")
- Random retrieval
- The policy is variant behavior abstract it.
- The behavior of the RAC is independent of exactly what the policy does.
- The RAC delegates the actual adding ("put") work to the policy.
- The RAC is only dependent on the existence of the policy, not what it does.
- The policy is a "strategy" for adding data to the RAC. See the Strategy design pattern.
- Strategy pattern vs. State pattern - so alike, yet so different!
The manufacturing of specific restricted access containers with specific insertion strategy will be done by concrete implementations of the following abstract factory interface.
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