timedcondition.java

来自「OpenJMS是一个开源的Java Message Service API 1.」· Java 代码 · 共 127 行

/**
 * Redistribution and use of this software and associated documentation
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 *
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 *    above copyright notice, this list of conditions and the
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 *    products derived from this Software without prior written
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 *    please contact [e-mail].
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 * 5. Due credit should be given to the Exolab Project
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 *
 * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 2005 (C) Exoffice Technologies Inc. All Rights Reserved.
 *
 * $Id: TimedCondition.java,v 1.1 2005/08/30 06:23:11 tanderson Exp $
 */
package org.exolab.jms.messagemgr;


/**
 * A timed {@link Condition}.
 *
 * @author <a href="mailto:[e-mail]">Tim Anderson</a>
 * @version $Revision: 1.1 $ $Date: 2005/08/30 06:23:11 $
 */
public class TimedCondition implements Condition {

    /**
     * The absolute time, in millseconds.
     */
    private final long _time;

    /**
     * Determines if the condition evaluates <code>true</code> while before or
     * after <code>time</code>.
     */
    private final boolean _before;


    /**
     * Construct a new <code>TimedCondition</code>.
     *
     * @param time   the absolute time, in milliseconds
     * @param before determines if the condition evaluates <code>true</code>
     *               while before or after <code>time</code>.
     */
    private TimedCondition(long time, boolean before) {
        _time = time;
        _before = before;
    }

    /**
     * Evaluates the condition.
     *
     * @return the value of the condition
     */
    public boolean get() {
        final long current = System.currentTimeMillis();
        if (_before) {
            return current < _time;
        }
        return current >= _time;
    }

    /**
     * Create a new <code>TimedCondition</code> that evaluates <code>true</code>
     * while the current time &lt; Now + time
     *
     * @param time the relative time, in milliseconds
     * @return a condition that evaluates <code>true</code> while the current
     * time &lt; Now + time
     */
    public static Condition before(long time) {
        return new TimedCondition(getAbsTime(time), true);
    }

    /**
     * Create a new <code>TimedCondition</code> that evaluates <code>true</code>
     * while the current time &gt;= Now + time
     *
     * @param time the relative time, in milliseconds
     * @return a condition that evaluates <code>true</code> while the current
     * time &gt;= Now + time
     */
    public static Condition after(long time) {
        return new TimedCondition(getAbsTime(time), false);
    }

    /**
     * Helper to return an absolute time in milliseconds, relative to now.
     *
     * @param time the relative time in milliseconds
     * @return the absolute time
     */
    private static long getAbsTime(long time) {
        return System.currentTimeMillis() + time;
    }
}