condition.java

JAVA实现的有限状态自动机。该软件适合Linux环境下安装运行。

/*****************************************************************************
 * net.openai.fsm.Condition
 *****************************************************************************
 * @author  JC on E
 * @date    9/18/2000
 * 2001 OpenAI Labs
 *****************************************************************************/

package net.openai.util.fsm;

import java.util.Vector;
import java.io.Serializable;


/**
 * This is the base class for all Conditions
 */
public abstract class Condition implements Serializable {

    /** A handle to our target State. */
    private State targetState;

    /** A handle to our source States. */
    private Vector sourceStates = new Vector();

    /**
     * Constructs a new Condition object.
     */
    public Condition() {
    }

    /**
     * Constructs a new Condition with the given target state.
     *
     * @param targetState The target state for this Condition.
     */
    public Condition(State targetState) {
	setTargetState(targetState);
    }

    /**
     * Sets the target state for this Condition.  This is the state that
     * will be the current state in the machine if this Condition is met.
     * <br><br>
     * NOTE: If the target state is null whenever this condition is being
     *       checked by the machine and it passes, then the result will
     *       be an UnhandledConditionException being thrown by the machine.
     *       Setting this to null is allowed because it will be necessary
     *       within a Graphical Building tool such as bean box or the 
     *       planned extensions to the net.openai.gui.graph package.
     *
     * @param targetState The new target state.
     */
    public final void setTargetState(State targetState) {
	this.targetState = targetState;
    }

    /**
     * Returns a handle to this Condition's current target state.
     *
     * @return This Condition's target state.
     */
    public final State getTargetState() {
	return targetState;
    }

    /**
     * Returns a handle to the source States of this Condition.  The source
     * States are the State that will check this Condition to see if it meets
     * the criterial passed in and then go on to the target State.
     *
     * @return The source states of this Condition or null if there are none.
     */
    public final Vector getSourceStates() {
	Vector returnValue = null;
	synchronized(sourceStates) {
	    returnValue = (Vector)sourceStates.clone();
	}
	return returnValue;
    }

    /**
     * Adds a source state to this Condition.
     *
     * @param state The state to add.
     */
    void addSourceState(State state) {
	if(state == null)
	    throw new NullPointerException("Cannot add null source state.");
	synchronized(sourceStates) {
	    if(!sourceStates.contains(state))
		sourceStates.addElement(state);
	}
    }

    /**
     * Removes a source state from this Condition.
     *
     * @param state The state to remove.
     */
    void removeSourceState(State state) {
	if(state == null)
	    return;
	synchronized(sourceStates) {
	    sourceStates.removeElement(state);
	}
    }

    /**
     * Called to check if the conditional meets the criteria defined by this
     * state.  This is the only method to implement in order to used this
     * interface.
     *
     * @param conditional The object to check.
     * @return Implementors should return <code>true</code> if this condition
     *         is met by the Object <code>conditional</code> and
     *         <code>false</code> otherwise.
     */
    public abstract boolean satisfiedBy(Object conditional);
}