方法三:内存文件映射

	public static long forImage(File f1, File f2) throws Exception {
		long time = new Date().getTime();
		int length = 2097152;
		FileInputStream in = new FileInputStream(f1);
		RandomAccessFile out = new RandomAccessFile(f2, "rw");
		FileChannel inC = in.getChannel();
		MappedByteBuffer outC = null;
		MappedByteBuffer inbuffer = null;
		byte[] b = new byte[length];
		while (true) {
			if (inC.position() == inC.size()) {
				inC.close();
				outC.force();
				out.close();
				return new Date().getTime() - time;
			}
			if ((inC.size() - inC.position()) < length) {
				length = (int) (inC.size() - inC.position());
			} else {
				length = 20971520;
			}
			b = new byte[length];
			inbuffer = inC.map(MapMode.READ_ONLY, inC.position(), length);
			inbuffer.load();
			inbuffer.get(b);
			outC = out.getChannel().map(MapMode.READ_WRITE, inC.position(),
					length);
			inC.position(b.length + inC.position());
			outC.put(b);
			outC.force();
		}
	}

实现方法:跟伤2个例子不一样,这里写文件流没有使用管道而是使用内存文件映射(假设文件f2在内存中).在循环中从f1的管道中读取数据到字节数组里,然后在像内存映射的f2文件中写数据.(读文件没有使用文件景象,有兴趣的可以回去试试,,我就不试了,估计会更快)

方法四:管道-管道

	public static long forChannel(File f1, File f2) throws Exception {
		long time = new Date().getTime();
		int length = 2097152;
		FileInputStream in = new FileInputStream(f1);
		FileOutputStream out = new FileOutputStream(f2);
		FileChannel inC = in.getChannel();
		FileChannel outC = out.getChannel();
		ByteBuffer b = null;
		while (true) {
			if (inC.position() == inC.size()) {
				inC.close();
				outC.close();
				return new Date().getTime() - time;
			}
			if ((inC.size() - inC.position()) < length) {
				length = (int) (inC.size() - inC.position());
			} else
				length = 2097152;
			b = ByteBuffer.allocateDirect(length);
			inC.read(b);
			b.flip();
			outC.write(b);
			outC.force(false);
		}
	}

这里实现方式与第3种实现方式很类似,不过没有使用内存影射.
 
下面是对49.3MB的文件进行拷贝的测试时间(毫秒)
Start Copy File...  file size:50290KB
CopyFile:b1.rmvb mode:forChannel  RunTime:3203
CopyFile:b1.rmvb mode:forImage  RunTime:3328
CopyFile:b1.rmvb mode:copyFile  RunTime:2172
CopyFile:b1.rmvb mode:copyFileNIO RunTime:1406
End Copy File!