Java NIO写大文件对比（win7和mac）

package rwbigfile;import java.io.ByteArrayInputStream;import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;import java.lang.reflect.Method;import java.nio.ByteBuffer;import java.nio.MappedByteBuffer;import java.nio.channels.Channels;import java.nio.channels.FileChannel;import java.nio.channels.FileChannel.MapMode;import java.nio.channels.ReadableByteChannel;import java.security.AccessController;import java.security.PrivilegedAction;import util.StopWatch;/** * NIO写大文件比较 * @author Will *  */public class WriteBigFileComparison {	// data chunk be written per time	private static final int DATA_CHUNK = 128 * 1024 * 1024; 	// total data size is 2G	private static final long LEN = 2L * 1024 * 1024 * 1024L; 		public static void writeWithFileChannel() throws IOException {		File file = new File("e:/test/fc.dat");		if (file.exists()) {			file.delete();		}		RandomAccessFile raf = new RandomAccessFile(file, "rw");		FileChannel fileChannel = raf.getChannel();		byte[] data = null;		long len = LEN;		ByteBuffer buf = ByteBuffer.allocate(DATA_CHUNK);		int dataChunk = DATA_CHUNK / (1024 * 1024);		while (len >= DATA_CHUNK) {			System.out.println("write a data chunk: " + dataChunk + "MB");			buf.clear(); // clear for re-write			data = new byte[DATA_CHUNK];			for (int i = 0; i < DATA_CHUNK; i++) {				buf.put(data[i]);			}			data = null;			buf.flip(); // switches a Buffer from writing mode to reading mode			fileChannel.write(buf);			fileChannel.force(true);			len -= DATA_CHUNK;		}		if (len > 0) {			System.out.println("write rest data chunk: " + len + "B");			buf = ByteBuffer.allocateDirect((int) len);			data = new byte[(int) len];			for (int i = 0; i < len; i++) {				buf.put(data[i]);			}			buf.flip(); // switches a Buffer from writing mode to reading mode, position to 0, limit not changed			fileChannel.write(buf);			fileChannel.force(true);			data = null;		}		fileChannel.close();		raf.close();	}	/**	 * write big file with MappedByteBuffer	 * @throws IOException	 */	public static void writeWithMappedByteBuffer() throws IOException {		File file = new File("e:/test/mb.dat");		if (file.exists()) {			file.delete();		}		RandomAccessFile raf = new RandomAccessFile(file, "rw");		FileChannel fileChannel = raf.getChannel();		int pos = 0;		MappedByteBuffer mbb = null;		byte[] data = null;		long len = LEN;		int dataChunk = DATA_CHUNK / (1024 * 1024);		while (len >= DATA_CHUNK) {			System.out.println("write a data chunk: " + dataChunk + "MB");			mbb = fileChannel.map(MapMode.READ_WRITE, pos, DATA_CHUNK);			data = new byte[DATA_CHUNK];			mbb.put(data);			data = null;			len -= DATA_CHUNK;			pos += DATA_CHUNK;		}		if (len > 0) {			System.out.println("write rest data chunk: " + len + "B");			mbb = fileChannel.map(MapMode.READ_WRITE, pos, len);			data = new byte[(int) len];			mbb.put(data);		}		data = null;		unmap(mbb);  // release MappedByteBuffer		fileChannel.close();	}		public static void writeWithTransferTo() throws IOException {		File file = new File("e:/test/transfer.dat");		if (file.exists()) {			file.delete();		}				RandomAccessFile raf = new RandomAccessFile(file, "rw");		FileChannel toFileChannel = raf.getChannel();				long len = LEN;		byte[] data = null;		ByteArrayInputStream bais = null;		ReadableByteChannel fromByteChannel = null;		long position = 0;		int dataChunk = DATA_CHUNK / (1024 * 1024);		while (len >= DATA_CHUNK) {			System.out.println("write a data chunk: " + dataChunk + "MB");						data = new byte[DATA_CHUNK];			bais = new ByteArrayInputStream(data);			fromByteChannel = Channels.newChannel(bais);						long count = DATA_CHUNK;			toFileChannel.transferFrom(fromByteChannel, position, count);						data = null;			position += DATA_CHUNK;			len -= DATA_CHUNK;		}				if (len > 0) {			System.out.println("write rest data chunk: " + len + "B");			data = new byte[(int) len];			bais = new ByteArrayInputStream(data);			fromByteChannel = Channels.newChannel(bais);						long count = len;			toFileChannel.transferFrom(fromByteChannel, position, count);		}				data = null;		toFileChannel.close();		fromByteChannel.close();	}		/**	 * 在MappedByteBuffer释放后再对它进行读操作的话就会引发jvm crash，在并发情况下很容易发生	 * 正在释放时另一个线程正开始读取，于是crash就发生了。所以为了系统稳定性释放前一般需要检	 * 查是否还有线程在读或写	 * @param mappedByteBuffer	 */	public static void unmap(final MappedByteBuffer mappedByteBuffer) {		try {			if (mappedByteBuffer == null) {				return;			}						mappedByteBuffer.force();			AccessController.doPrivileged(new PrivilegedAction<Object>() {				@Override				@SuppressWarnings("restriction")				public Object run() {					try {						Method getCleanerMethod = mappedByteBuffer.getClass()								.getMethod("cleaner", new Class[0]);						getCleanerMethod.setAccessible(true);						sun.misc.Cleaner cleaner = 								(sun.misc.Cleaner) getCleanerMethod									.invoke(mappedByteBuffer, new Object[0]);						cleaner.clean();											} catch (Exception e) {						e.printStackTrace();					}					System.out.println("clean MappedByteBuffer completed");					return null;				}			});		} catch (Exception e) {			e.printStackTrace();		}	}	public static void main(String[] args) throws IOException {		StopWatch sw = new StopWatch();				sw.startWithTaskName("write with file channel's write(ByteBuffer)");		writeWithFileChannel();		sw.stopAndPrint();				sw.startWithTaskName("write with file channel's transferTo");		writeWithTransferTo();		sw.stopAndPrint();				sw.startWithTaskName("write with MappedByteBuffer");		writeWithMappedByteBuffer();		sw.stopAndPrint();	}}

import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;import java.nio.MappedByteBuffer;import java.nio.channels.FileChannel;public class MappedFile {		// 文件名	private String fileName;	// 文件所在目录路径	private String fileDirPath;	// 文件对象	private File file;	private MappedByteBuffer mappedByteBuffer;	private FileChannel fileChannel;	private boolean boundSuccess = false;	// 文件最大只能为50MB	private final static long MAX_FILE_SIZE = 1024 * 1024 * 50;		// 最大的脏数据量512KB,系统必须触发一次强制刷	private long MAX_FLUSH_DATA_SIZE = 1024 * 512;	// 最大的刷间隔,系统必须触发一次强制刷	private long MAX_FLUSH_TIME_GAP = 1000;	// 文件写入位置	private long writePosition = 0;	// 最后一次刷数据的时候	private long lastFlushTime;	// 上一次刷的文件位置	private long lastFlushFilePosition = 0;		public MappedFile(String fileName, String fileDirPath) {		super();		this.fileName = fileName;		this.fileDirPath = fileDirPath;		this.file = new File(fileDirPath + "/" + fileName);		if (!file.exists()) {			try {				file.createNewFile();			} catch (IOException e) {				e.printStackTrace();			}		}			}	/**	 * 	 * 内存映照文件绑定	 * @return	 */	public synchronized boolean boundChannelToByteBuffer() {		try {			RandomAccessFile raf = new RandomAccessFile(file, "rw");			this.fileChannel = raf.getChannel();		} catch (Exception e) {			e.printStackTrace();			this.boundSuccess = false;			return false;		}		try {			this.mappedByteBuffer = this.fileChannel					.map(FileChannel.MapMode.READ_WRITE, 0, MAX_FILE_SIZE);		} catch (IOException e) {			e.printStackTrace();			this.boundSuccess = false;			return false;		}		this.boundSuccess = true;		return true;	}		/**	 * 写数据：先将之前的文件删除然后重新	 * @param data	 * @return	 */	public synchronized boolean writeData(byte[] data) {				return false;	}		/**	 * 在文件末尾追加数据	 * @param data	 * @return	 * @throws Exception	 */	public synchronized boolean appendData(byte[] data) throws Exception {		if (!boundSuccess) {			boundChannelToByteBuffer();		}				writePosition = writePosition + data.length;		if (writePosition >= MAX_FILE_SIZE) {  // 如果写入data会超出文件大小限制，不写入			flush();			writePosition = writePosition - data.length;			System.out.println("File=" 								+ file.toURI().toString() 								+ " is written full.");			System.out.println("already write data length:" 								+ writePosition								+ ", max file size=" + MAX_FILE_SIZE);			return false;		}		this.mappedByteBuffer.put(data);		// 检查是否需要把内存缓冲刷到磁盘		if ( (writePosition - lastFlushFilePosition > this.MAX_FLUSH_DATA_SIZE)			 ||			 (System.currentTimeMillis() - lastFlushTime > this.MAX_FLUSH_TIME_GAP			 && writePosition > lastFlushFilePosition) ) {			flush();  // 刷到磁盘		}				return true;	}	public synchronized void flush() {		this.mappedByteBuffer.force();		this.lastFlushTime = System.currentTimeMillis();		this.lastFlushFilePosition = writePosition;	}	public long getLastFlushTime() {		return lastFlushTime;	}	public String getFileName() {		return fileName;	}	public String getFileDirPath() {		return fileDirPath;	}	public boolean isBundSuccess() {		return boundSuccess;	}	public File getFile() {		return file;	}	public static long getMaxFileSize() {		return MAX_FILE_SIZE;	}	public long getWritePosition() {		return writePosition;	}	public long getLastFlushFilePosition() {		return lastFlushFilePosition;	}	public long getMAX_FLUSH_DATA_SIZE() {		return MAX_FLUSH_DATA_SIZE;	}	public long getMAX_FLUSH_TIME_GAP() {		return MAX_FLUSH_TIME_GAP;	}}