Java tutorial
/* * Copyright 2014 Sam Leroux <sam.leroux@ugent.be>. * * Licensed 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 be.ugent.tiwi.sleroux.newsrec.newsreclib.newsFetch.storm.bolts.trendDetect; import backtype.storm.utils.Time; import org.apache.commons.collections.buffer.CircularFifoBuffer; /** * This class tracks the time-since-last-modify of a "thing" in a rolling * fashion. * <p/> * For example, create a 5-slot tracker to track the five most recent * time-since-last-modify. * <p/> * You must manually "mark" that the "something" that you want to track -- in * terms of modification times -- has just been modified. */ public class NthLastModifiedTimeTracker { private static final int MILLIS_IN_SEC = 250; private final CircularFifoBuffer lastModifiedTimesMillis; /** * * @param numTimesToTrack */ public NthLastModifiedTimeTracker(int numTimesToTrack) { if (numTimesToTrack < 1) { throw new IllegalArgumentException( "numTimesToTrack must be greater than zero (you requested " + numTimesToTrack + ")"); } lastModifiedTimesMillis = new CircularFifoBuffer(numTimesToTrack); initLastModifiedTimesMillis(); } private void initLastModifiedTimesMillis() { long nowCached = now(); for (int i = 0; i < lastModifiedTimesMillis.maxSize(); i++) { lastModifiedTimesMillis.add(Long.valueOf(nowCached)); } } private long now() { return Time.currentTimeMillis(); } /** * * @return */ public int secondsSinceOldestModification() { long modifiedTimeMillis = ((Long) lastModifiedTimesMillis.get()).longValue(); return (int) ((now() - modifiedTimeMillis) / MILLIS_IN_SEC); } /** * */ public void markAsModified() { updateLastModifiedTime(); } private void updateLastModifiedTime() { lastModifiedTimesMillis.add(now()); } }