如果對于Fork/Join不了解的話可以參考這里：http://www.infoq.com/cn/articles/fork-join-introduction、http://ifeve.com/fork-join-1/、http://www.iteye.com/topic/643724 。主要代碼如下：
package com.zkn.fullstacktraining.seventh;import com.google.common.collect.Lists;import javafx.util.Pair;import java.io.IOException;import java.nio.file.Files;import java.nio.file.Path;import java.nio.file.Paths;import java.util.List;import java.util.Optional;import java.util.concurrent.ExecutionException;import java.util.concurrent.ForkJoinPool;import java.util.concurrent.Future;import java.util.concurrent.RecursiveTask;import java.util.stream.Collectors;import java.util.stream.IntStream;/** * Created by wb-zhangkenan on 2017/2/6. * 通過Fork/Join的方式來統計某個字符串在某個文件夾下的文件中出現的次數 */public class SearchStringByForkJoin extends RecursiveTask<List<Pair<String, Integer>>> { //任務的閥值 PRivate static final int THRESHOLD = 5; //任務區間的開始值 private int start; //任務區間的結束值 private int end; //所有的路徑信息 private List<Path> allPaths; public SearchStringByForkJoin(int start, int end, List<Path> allPaths) { this.start = start; this.end = end; this.allPaths = allPaths; } public static void main(String[] args) { ForkJoinPool forkJoinPool = new ForkJoinPool(); try { List<Path> pathList = Files.walk(Paths.get("D://CUST//WORK//Exercises//FullStackTraining//src//main//java//com//zkn"), 4) .filter(file -> !Files.isDirectory(file) && file.toString().endsWith("java")) .collect(Collectors.toList()); SearchStringByForkJoin searchStringByForkJoin = new SearchStringByForkJoin(0, pathList.size(), pathList); Future<List<Pair<String, Integer>>> result = forkJoinPool.submit(searchStringByForkJoin); List<Pair<String, Integer>> pairList = result.get(); pairList.stream() .filter(pair -> pair.getValue() > 0) .sorted((s1, s2) -> Integer.compare(s2.getValue(), s1.getValue())) .forEach(pair -> System.out.println(String.format("%d次出現在%s文件中", pair.getValue(), pair.getKey().toString()))); forkJoinPool.shutdown(); } catch (IOException e) { e.printStackTrace(); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } } /** * The main computation performed by this task. * @return the result of the computation */ @Override protected List<Pair<String, Integer>> compute() { List<Pair<String, Integer>> pairList = Lists.newArrayList(); boolean canCompute = end - start <= THRESHOLD; if (canCompute) { pairList = IntStream.range(start, end + 1).mapToObj(i -> { //到集合的結尾了 if (i == allPaths.size()) return new Pair<>("", 0); int sum = 0; try { Optional optional = Files.lines(allPaths.get(i)).map(file -> { int count = 0; int flag = file.indexOf("main"); if (flag >= 0) { do { count++; } while ((flag = file.indexOf("main", flag + 1)) > 0); } return count; }).reduce(Integer::sum); sum = optional.isPresent() ? (int) optional.get() : 0; } catch (IOException e) { e.printStackTrace(); } return new Pair<>(allPaths.get(i).toString(), sum); }).collect(Collectors.toList()); } else { //取中間值 int middle = (end + start) / 2; //創建Fork子任務 SearchStringByForkJoin leftFork = new SearchStringByForkJoin(start, middle, allPaths); //創建Fork子任務 SearchStringByForkJoin rightFork = new SearchStringByForkJoin(middle + 1, end, allPaths); //執行子任務 leftFork.fork(); rightFork.fork(); //合并子任務的結果集 pairList.addAll(leftFork.join()); pairList.addAll(rightFork.join()); } return pairList; }}新聞熱點
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