dataset.java

来自「这是一个以JAVA编写的程序,本人还没有试过,是一个简单的温度控制系统」· Java 代码 · 共 188 行

package net.sf.dz.controller;

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * Entity supporting the data sampling.
 *
 * @author Copyright &copy; <a href="mailto:[e-mail]"> Vadim Tkachenko</a> 2001-2002
 * @version $Id: DataSet.java,v 1.5 2004/06/28 20:35:46 vtt Exp $
 */
public class DataSet {

    /**
     * The data set.
     *
     * The key is sampling time, the value is sample value.
     */
    private SortedMap dataSet = new TreeMap();

    /**
     * The expiration interval.
     *
     * Values older than the last key by this many milliseconds are expired.
     */
    private long expirationInterval;

    /**
     * Strictness.
     *
     * If this is set to true, the {@link #record record()} will not accept
     * values for the time less than already recorded, and {@link #record
     * record()} will throw <code>IllegalArgumentException</code>.
     *
     * <p>
     *
     * This is not necessarily a good thing.
     */
    private boolean strict = false;

    /**
     * Create the instance.
     *
     * @param expirationInterval How many milliseconds to keep the data.
     *
     * @exception IllegalArgumentException if the expiration interval is
     * non-positive (<= 0). Be careful with the short intervals, it's going
     * to be your fault, not mine.
     */
    public DataSet(final long expirationInterval) {

        if (expirationInterval <= 0) {

            throw new IllegalArgumentException("Expiration interval must be positive, value given is " + expirationInterval);
        }

        this.expirationInterval = expirationInterval;
    }

    /**
     * Set strictness.
     *
     * @param strict If set to true, out-of-order updates will not be
     * accepted.
     */
    public final void setStrict(final boolean strict) {

        this.strict = strict;
    }

    /**
     * Get the expiration interval.
     *
     * @return Expiration interval, milliseconds.
     */
    public final long getExpirationInterval() {

        return expirationInterval;
    }

    /**
     * Record the sample.
     *
     * @param millis Absolute time, milliseconds.
     *
     * @param value The sample value.
     */
    public final synchronized void record(final long millis, final double value) {

        // We don't care if there was a value associated with the given key
        // before, so we return nothing.

        if (strict) {

            try {

                Long lastKey = (Long) dataSet.lastKey();

                if (lastKey.longValue() >= millis) {

                    throw new IllegalArgumentException("Data element out of sequence: last key is " + lastKey + ", key being added is " + millis);
                }

            } catch (NoSuchElementException nseex) {

                // We're fine. This means that there was no previous entry,
                // therefore, the current one will not be out of order.
            }
        }

        dataSet.put(new Long(millis), new Double(value));

        expire();

        //System.err.println("DataSet@" + hashCode() + ": " + dataSet.size());
    }

    /**
     * Expire all the data elements older than the last by {@link
     * #expirationInterval expiration interval}.
     */
    protected final void expire() {

        try {

            Long lastKey = (Long) dataSet.lastKey();
            Long expireBefore = new Long(lastKey.longValue() - expirationInterval);

            SortedMap expireMap = dataSet.headMap(expireBefore);

            for (Iterator i = expireMap.keySet().iterator(); i.hasNext();) {

                Object found = i.next();
                i.remove();

                //System.err.println("Expired: " + found + ", left: " + dataSet.size());
            }

        } catch (NoSuchElementException nseex) {

           // We're fine, the map is empty
        }
    }

    /**
     * @return Iterator on the time values for the data entries.
     */
    public final Iterator iterator() {

        return dataSet.keySet().iterator();
    }

    /**
     * Get the data set size.
     *
     * @return {@link #dataSet dataSet} size.
     */
    public final long size() {

        return dataSet.size();
    }

    /**
     * Get the value recorded at the given time.
     *
     * @param time Time to look up the data for. Must be exact, otherwise,
     * exception will be thrown.
     *
     * @return Value recorded at the given time.
     *
     * @exception NoSuchElementException if the value for the given time is
     * not in the set.
     */
    public final double get(final long time) {

        Double result = (Double) dataSet.get(new Long(time));

        if (result == null) {

            throw new NoSuchElementException("No value for time " + time);
        }

        return result.doubleValue();
    }
}