我有一个程序加载缓慢,我猜这是由于我一开始必须加载的图像资源量所致。我认为多线程会有所帮助,但现在我不太确定。这是我的自动多线程方法。
private static Thread[] t;
private static int currentThreads;
public static void loadWithThreads(Object[] array, IntegerRunnable r) {
final int threads = Runtime.getRuntime().availableProcessors();
t = new Thread[threads];
for (int i = 0; i < threads; i ++) {
t[i] = new Thread("HMediaConverter") {
final int id = currentThreads;
int items = (array.length / threads) * currentThreads;
@Override
public void run() {
super.run();
for (int i = items; i < (items + (array.length / threads)); i ++) {
r.run(i);
}
//Recycle this thread so it can be used for another time.
try {
t[id].join();
lock.notifyAll();
currentThreads --;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
t[i].setPriority(Thread.MAX_PRIORITY);
t[i].start();
currentThreads ++;
}
}
这是我的图像加载代码:
public static ImageIcon loadImageIcon(String path) {
return new ImageIcon(ImageIO.read(Tools.class.getClassLoader().getResource(path));
}
当然有办法加快速度吗?我在完美的 Intel i5 上运行它,它不应该这么慢,所以它一定是我的代码。
正在加载 113 张图片,总共 159.14mb...
public static void loadWithoutThreads(File[] array) {
for (File file : array) {
try {
ImageIO.read(file);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
花了~15秒
With...
public static void loadWithThreads(File[] array) {
final int threads = Runtime.getRuntime().availableProcessors();
t = new Thread[threads];
CountDownLatch latch = new CountDownLatch(threads);
for (int i = 0; i < threads; i++) {
t[i] = new Thread("HMediaConverter") {
final int id = currentThreads;
int items = (array.length / threads) * currentThreads;
@Override
public void run() {
try {
System.out.println("Starting " + id);
for (int i = items; i < (items + (array.length / threads)); i++) {
try {
System.out.println(i + ": " + array[i]);
ImageIO.read(array[i]);
} catch (IOException ex) {
ex.printStackTrace();
}
}
} finally {
latch.countDown();
}
}
};
t[i].setPriority(Thread.MAX_PRIORITY);
System.out.println("Start " + i);
t[i].start();
currentThreads++;
}
try {
latch.await();
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
花了~11秒
With...
public static void loadWithExecutor(File[] images) {
ExecutorService service = Executors.newFixedThreadPool(2);
List<ImageLoadingTask> tasks = new ArrayList<>(images.length);
for (File file : images) {
tasks.add(new ImageLoadingTask(file));
}
try {
List<Future<BufferedImage>> results = service.invokeAll(tasks);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
service.shutdown();
}
public static class ImageLoadingTask implements Callable<BufferedImage> {
private File file;
public ImageLoadingTask(File file) {
this.file = file;
}
@Override
public BufferedImage call() throws Exception {
return ImageIO.read(file);
}
}
Took ~7s
The ExecutorService
效率更高,因为当一个线程处理较大文件时,另一个线程可以处理许多小文件。这是通过池化那些在需要时不做任何工作的线程来实现的,允许一个线程执行大量短期工作,而其他线程也很忙。你不需要等待那么久
看一下执行者更多细节
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