知识库--Concurrency+ThreadPool+Executors(79)

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阻塞系数=0.9 四核处理器（该实例模拟多线程IO密集型模型）

public abstract class AbstractNAV {    public static Map<String, Integer> readTickers() throws IOException {        final BufferedReader reader =                new BufferedReader(new FileReader("C:\\Users\\ang\\Desktop\\stocks.txt"));        final Map<String, Integer> stocks = new HashMap<String, Integer>();        String stockInfo = null;        while((stockInfo = reader.readLine()) != null) {            final String[] stockInfoData = stockInfo.split(",");            final String stockTicker = stockInfoData[0];            final Integer quantity = Integer.valueOf(stockInfoData[1]);            stocks.put(stockTicker, quantity);        }        return stocks;    }    public void timeAndComputeValue()            throws ExecutionException, InterruptedException, IOException {        final long start = System.nanoTime();        final Map<String, Integer> stocks = readTickers();        final double nav = computeNetAssetValue(stocks);        final long end = System.nanoTime();        final String value = new DecimalFormat("$##,##0.00").format(nav);        System.out.println("Your net asset value is " + value);        System.out.println("Time (seconds) taken " + (end - start)/1.0e9);    }    public abstract double computeNetAssetValue(            final Map<String, Integer> stocks)            throws ExecutionException, InterruptedException, IOException;}

public class Concurrent extends AbstractNAV {    public double computeNetAssetValue(final Map<String, Integer> stocks)            throws InterruptedException, ExecutionException {        final int numberOfCores = Runtime.getRuntime().availableProcessors();        final double blockingCoefficient = 0.9;        final int poolSize = (int) (numberOfCores / (1 - blockingCoefficient));        System.out.println("Number of Cores available is " + numberOfCores);        System.out.println("Pool size is " + poolSize);        final List<Callable<Double>> partitions = new ArrayList<Callable<Double>>();        for (final String ticker : stocks.keySet()) {            partitions.add(new Callable<Double>() {                public Double call() throws Exception {                    return stocks.get(ticker) * YahooFinance.getPrice(ticker);                }            });        }        final ExecutorService executorPool = Executors.newFixedThreadPool(poolSize);        final List<Future<Double>> valueOfStocks =                executorPool.invokeAll(partitions, 10000, TimeUnit.SECONDS);        double netAssetValue = 0.0;        for (final Future<Double> valueOfAStock : valueOfStocks)            netAssetValue += valueOfAStock.get();        executorPool.shutdown();        return netAssetValue;    }    public static void main(final String[] args) throws ExecutionException, InterruptedException, IOException {        new Concurrent().timeAndComputeValue();    }}

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