對於讀檔案NIO與IO誰快？

        如果加一些複雜環境，然後再讓他們去讀檔案呢？

        為了得到這個答案，我做了兩組實驗，首先是直接單執行緒去讀一個很大的檔案，分別通過NIO和IO去讀：

/**
	 * nio 讀
	 * 
	 * @param fileName
	 */
	public static void readFileWithNIO(String fileName) {
		try {
			long now = new Date().getTime();
			FileInputStream fs = new FileInputStream(fileName);
			FileChannel fc = fs.getChannel();
			ByteBuffer bb = ByteBuffer.allocate(1024);
			while (true) {
				bb.clear();
				int count = fc.read(bb);
				if (count == -1)
					break;
				// System.out.println(new String(bb.array()));
			}

			fc.close();
			fs.close();
			System.out.println("nio read time:" + (new Date().getTime() - now)
					+ "ms");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
 

public static void readFileWithIO(String fileName) {

		try {
			long now = new Date().getTime();
			FileInputStream fs = new FileInputStream(fileName);
			byte bb[] = new byte[1024];
			while (fs.read(bb) != -1) {
				// System.out.println(new String(bb));
			}
			fs.close();
			System.out.println("io read time:" + (new Date().getTime() - now)
					+ "ms");
		} catch (Exception e) {
			e.printStackTrace();
		}

	}
 

      對於這個結論並不奇怪，因為NIO的特性明確標明是 非阻塞。單執行緒讀檔案，很難體現這個非阻塞的特點，非阻塞的言外之意是可以幹別的事情。於是，我做了如下實驗，我用多執行緒去讀檔案，也是分別用IO和NIO，這個時候的測試結果發現NIO和IO已經非常接近了，但是還是IO快。於是，我有增加了額外的執行緒在讀檔案的同時去幹一些其他的事情，這個時候，我終於發現NIO比IO快了，程式碼如下：

public static void readFileWithNIOMultThread(String fileName) {
		try {
			long now = new Date().getTime();
			FileInputStream fs = new FileInputStream(fileName);
			final FileChannel fc = fs.getChannel();

			class TestThread implements Runnable {
				public void run() {
					ByteBuffer bb = ByteBuffer.allocate(102400);
					try {
						while (true) {
							bb.clear();
							int count = fc.read(bb);
							if (count == -1)
								break;
							// System.out.println(new String(bb.array()));
							// Thread.sleep((long)(Math.random() * 1000));
						}
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			}
			ArrayList<Thread> list = new ArrayList<Thread>();

			for (int i = 0; i < 10; i++) {
				Thread tmp = new Thread(new TestThread());
				list.add(tmp);
				tmp.start();
			}
			
			for (int i = 0; i < 10; i++) {
				Thread tmp = new Thread(new Runnable() {

					public void run() {
						try {
							for(int i=0;i<1000;i++){
								System.out.println(i);
							}
						} catch (Exception e) {
							e.printStackTrace();
						}

					}
				});
				list.add(tmp);
				tmp.start();
			}

			for (Thread t : list) {
				t.join();
			}

			fc.close();
			fs.close();
			System.out.println("nio read time:" + (new Date().getTime() - now)
					+ "ms");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
 

public static void readFileWithIOMultThreads(String fileName) {
		long now = new Date().getTime();
		try {
			final FileInputStream fs = new FileInputStream(fileName);
			class TestThread implements Runnable {
				public void run() {
					byte bb[] = new byte[102400];
					try {
						while (fs.read(bb) != -1) {
							// System.out.println(new String(bb));
							// Thread.sleep((long)(Math.random() * 1000));
						}
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			}

			ArrayList<Thread> list = new ArrayList<Thread>();

			for (int i = 0; i < 10; i++) {
				Thread tmp = new Thread(new TestThread());
				list.add(tmp);
				tmp.start();
			}

			for (int i = 0; i < 10; i++) {
				Thread tmp = new Thread(new Runnable() {

					public void run() {
						try {
							for(int i=0;i<1000;i++){
								System.out.println(i);
							}
						} catch (Exception e) {
							e.printStackTrace();
						}

					}
				});
				list.add(tmp);
				tmp.start();
			}

			for (Thread t : list) {
				t.join();
			}

			fs.close();

			System.out.println("io read time:" + (new Date().getTime() - now)
					+ "ms");
		} catch (Exception e) {
			e.printStackTrace();
		}

	}