Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.util;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

A synchronized implementation of  SimpleDateFormat which uses caching internally.
Author:
Ceki Gülcü
Since:
0.9.29/**
 * A synchronized implementation of  SimpleDateFormat which uses caching internally.
 *
 * @author Ceki Gülcü
 * @since 0.9.29
 */
public class CachingDateFormatter {

    long lastTimestamp = -1;
    String cachedStr = null;
    final SimpleDateFormat sdf;

    public CachingDateFormatter(String pattern) {
        sdf = new SimpleDateFormat(pattern);
    }

    public final String format(long now) {

        // SimpleDateFormat is not thread safe.

        // See also the discussion in http://jira.qos.ch/browse/LBCLASSIC-36
        // DateFormattingThreadedThroughputCalculator and SelectiveDateFormattingRunnable
        // are also noteworthy

        // The now == lastTimestamp guard minimizes synchronization
        synchronized (this) {
            if (now != lastTimestamp) {
                lastTimestamp = now;
                cachedStr = sdf.format(new Date(now));
            }
            return cachedStr;
        }
    }

    public void setTimeZone(TimeZone tz) {
        sdf.setTimeZone(tz);
    }
}