think in java - I/O - NIO

# what's NIO

It's intriduced in JDK 1.4, has one goal: speed! Rapidly moving large amounts of data.

Actually, the 'old IO' have been reimplemented using NIO.

# why NIO is fast?

The speed comes from using structure which is closer to the operating system's way of performing IO: 

- Channel: like coal mine containing the seam of coal(data)

- Buffer: like the cart you send into the mine, the cart come back full of coal, we get coal from cart.

# FileChannel vs BufferInputStream/BufferOutputStream

after testing, I found that FileChannel is slower, super disappointed~~~

especially 'transferTo()' method is super slow '''

# view buffer

- which allows you to look at an underlying ByteBuffer through the window of a particular primitive type.

- ByteBuffer is still the actual storage that’s "backing" the view

- so any changes you make to the view are reflected in modifications to the data in the ByteBuffer.

ByteBuffer buffer = ByteBuffer.allocate(1024);
// intBuffer
IntBuffer intBuffer = buffer.asIntBuffer();
intBuffer.put(new int[] {0,1,2,3,4,5,6,7,8,9});
intBuffer.put(/*index*/ 0, /*value*/ 100);

# File locking

- File locking allows you to synchronize access to a file as a shared resource.

- two threads that contend for the same file may be in different JVMs, or one may be a Java thread and the other some native thread in the operating system

public class FileLocking {
	public static void main(String[] args) throws Exception {
		FileOutputStream fos = new FileOutputStream("file.txt");
		FileLock fLock = fos.getChannel().tryLock();
		
		if (null != fLock) {
			System.out.println("File locked");
			TimeUnit.SECONDS.sleep(1);
			fLock.release();
			System.out.println("Release lock");
		}
		fos.close();
	}
}