GraphSolver.java

package edu.hawaii.ics.yucheng;

import java.util.ArrayList;

/**
 * An abstract path that provides base functionality for graph solvers.
 */
abstract class GraphSolver {

    /** A flag indicating if the solution is canceled. */
    private boolean                        myCanceled;

    /** A collection of listeners. */
    private final ArrayList<GraphListener> myListeners;


    /**
     * Initializes a new instance of the class.
     */
    public GraphSolver() {
        myListeners = new ArrayList<GraphListener>();
    }


    /**
     * Adds a graph listener.
     * 
     * @param listener The listener.
     */
    public void addGraphListener(final GraphListener listener) {
        if (listener == null)
            throw new NullPointerException("listener");

        myListeners.add(listener);
    }


    /**
     * Returns true if the solver has been canceled.
     * 
     * @return True if the solver has been canceled.
     */
    public boolean isCanceled() {
        synchronized (this) {
            return myCanceled;
        }
    }


    /**
     * Removes a graph listener.
     * 
     * @param listener The graph listener.
     */
    public void removeGraphListener(final GraphListener listener) {
        if (listener == null)
            throw new NullPointerException("listener");

        myListeners.remove(listener);
    }


    /**
     * Reports progress from the solver to the listeners.
     * 
     * @param percent The percent complete.
     * 
     * @param solution The solution.
     */
    protected void reportProgress(final Integer percent,
        final GraphSolution solution) {

        for (final GraphListener listener : myListeners)
            listener.progress(percent, solution);
    }


    /**
     * Sets the canceled flag of the solver.
     * 
     * @param canceled True if the solver is canceled.
     */
    public void setCanceled(final boolean canceled) {
        synchronized (this) {
            myCanceled = canceled;
        }
    }


    /**
     * Solves a specified graph and returns the solution.
     * 
     * @param graph The graph input.
     * 
     * @return The solution.
     */
    protected abstract GraphSolution solve(final Graph graph);
}