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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package com.republicate.slf4j.util;

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

/**
 * A synchronized implementation of SimpleDateFormat which uses caching internally.
 *
 * @author Ceki Gücü
 */
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 note worthy
        
        // 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);
    }
}