actionlist.java

PIY(Program It Yourself)是一个基于Java的应用程序开发环境

package piy;

import java.util.*;
import java.io.*;

/**
* Represents a list of Actions which are executed sequentially.
* @author David Vivash
* @version 1.0, 19/11/00
*/
public class ActionList implements Serializable
{
	private ArrayList actions = new ArrayList(4); //initial size set to 4
	private HashMap returns = new HashMap(4);

	/**
	* Add an action to the end of the list
	* @param action the action to add
	*/
	public void add(PIYAction action) { actions.add(action); }

	/**
	* Insert an action into a specific position. ie. 0 = start of the list, size() = end of list.
	* @param index a value between 0 and size() inclusive
	* @param action the action to insert
	* @throws IndexOutOfBoundsException if size() < index < 0
	*/
	public void add(int index, PIYAction action) throws IndexOutOfBoundsException
	{ actions.add(index, action); }

	/**
	* Removes the action at the specified index from the list.  Subsequent actions are shifted left (ie.
	* their indices ar decremented.
	* @param index a value between 0 and size()-1 represting the index of the action to be removed
	* @throws IndexOutOfBoundsException if size() <= index < 0 
	*/
	public void remove(int index) throws IndexOutOfBoundsException { 
		returns.remove(get(index));
		actions.remove(index); 
	}

	/**
	* Removes the specefied action from this list, providing the action is defined in this list.
	* @param action the action to remove
	* @return the position in the list that the action was at before it was removed, or -1 if the 
	* action wasn't in the list
	*/
	public int removeAction(PIYAction action) {
		int index = getIndex(action);
		if (index > -1) remove(index);

		return index;
	}

	/**
	* Retrieves the number of actions stored in the actionlist.
	* @return the length of this actionlist (number of actions)
	*/
	public int size() { return actions.size(); }

	/**
	* Get the action at position pos.
	* @param pos the index of the item in the list to retrieve (numbering starts at zero)
	* @return the action at position pos (could be null)
	* @throws IndexOutOfBoundsException if size() <= pos > 0
	*/
	public PIYAction get(int pos) throws IndexOutOfBoundsException
	{ return (PIYAction)actions.get(pos); }

	/**
	* Gets the index of the specified action, ie. where in the list the specified action is located.
	* If the action is not found in the list, -1 is returned.
	* @param action the action to find
	* @return the position of the action in the list, or -1 if the action is not in the list
	*/
	public int getIndex(PIYAction action) {
		for (int i=0; i<size(); i++)
			if (actions.get(i) == action) return i;

		return -1;
	}

	/**
	* Gets where the specified action sends its return value to.
	* @param action the action returning a value
	* @return the Property placeholder where the action value will be stored
	*/
	public Property getReturn(PIYAction action) {
		return (Property)returns.get(action);
	}
	
	/**
	* Set the place where a specified action will send its result value.
	* @param action the action returning the value
	* @param property the place the value will be stored
	*/
	public void setReturn(PIYAction action, Property property) {
		returns.put(action, property);
	}

	/**
	* executes the actions in the action list sequentially.
	*/
	public void execute()
	{
		Iterator i = actions.iterator();
		PIYAction action = null;
		Object returnValue = null;
		Property returnPlace = null;
		
		while (i.hasNext()) {
			action = (PIYAction)i.next();
			if (action != null) {
				returnValue = action.execute();
				if ( (returnPlace = (Property)returns.get(action)) != null)
					returnPlace.setValue(returnValue);
			}

		}
	}
}