public class RandomAccessFile implements DataOutput, DataInput {	public final byte readByte() throws IOException {		int ch = this.read();		if (ch < 0)			throw new EOFException();		return (byte)(ch);	}	public native int read() throws IOException; 	public final void writeByte(int v) throws IOException {		write(v);	} 	public native void write(int b) throws IOException; }

public class BufferedInputStream extends FilterInputStream {	private static int defaultBufferSize = 2048; 	protected byte buf[]; // 建立读缓存区	public BufferedInputStream(InputStream in, int size) {		super(in);        		if (size <= 0) {			throw new IllegalArgumentException("Buffer size <= 0");		}		buf = new byte[size];	}	public synchronized int read() throws IOException {		ensureOpen();		if (pos >= count) {			fill();			if (pos >= count)				return -1;		}		return buf[pos++] & 0xff; // 直接从BUF[]中读取	} 	private void fill() throws IOException {	if (markpos < 0)	    pos = 0;		/* no mark: throw away the buffer */	else if (pos >= buf.length)	/* no room left in buffer */	    if (markpos > 0) {	/* can throw away early part of the buffer */		int sz = pos - markpos;		System.arraycopy(buf, markpos, buf, 0, sz);		pos = sz;		markpos = 0;	    } else if (buf.length >= marklimit) {		markpos = -1;	/* buffer got too big, invalidate mark */		pos = 0;	/* drop buffer contents */	    } else {		/* grow buffer */		int nsz = pos * 2;		if (nsz > marklimit)		    nsz = marklimit;		byte nbuf[] = new byte[nsz];		System.arraycopy(buf, 0, nbuf, 0, pos);		buf = nbuf;	    }	count = pos;	int n = in.read(buf, pos, buf.length - pos);	if (n > 0)	    count = n + pos;	}}

public class BufferedOutputStream extends FilterOutputStream {   protected byte buf[]; // 建立写缓存区   public BufferedOutputStream(OutputStream out, int size) {		super(out);		if (size <= 0) {			throw new IllegalArgumentException("Buffer size <= 0");		}		buf = new byte[size];    } public synchronized void write(int b) throws IOException {		if (count >= buf.length) {	   		flushBuffer();		}		buf[count++] = (byte)b; // 直接从BUF[]中读取   }   private void flushBuffer() throws IOException {		if (count > 0) {			out.write(buf, 0, count);			count = 0;		}   }}

public class BufferedRandomAccessFile extends RandomAccessFile {//  byte read(long pos)：读取当前文件POS位置所在的字节//  bufstartpos、bufendpos代表BUF映射在当前文件的首/尾偏移地址。//  curpos指当前类文件指针的偏移地址。    public byte read(long pos) throws IOException {        if (pos < this.bufstartpos || pos > this.bufendpos ) {            this.flushbuf();            this.seek(pos);            if ((pos < this.bufstartpos) || (pos > this.bufendpos))                 throw new IOException();        }        this.curpos = pos;        return this.buf[(int)(pos - this.bufstartpos)];    }// void flushbuf()：bufdirty为真，把buf[]中尚未写入磁盘的数据，写入磁盘。    private void flushbuf() throws IOException {        if (this.bufdirty == true) {            if (super.getFilePointer() != this.bufstartpos) {                super.seek(this.bufstartpos);            }            super.write(this.buf, 0, this.bufusedsize);            this.bufdirty = false;        }    }// void seek(long pos)：移动文件指针到pos位置，并把buf[]映射填充至POS所在的文件块。    public void seek(long pos) throws IOException {        if ((pos < this.bufstartpos) || (pos > this.bufendpos)) { // seek pos not in buf            this.flushbuf();            if ((pos >= 0) && (pos <= this.fileendpos) && (this.fileendpos != 0)) {   // seek pos in file (file length > 0)            	  this.bufstartpos =  pos * bufbitlen / bufbitlen;                this.bufusedsize = this.fillbuf();            } else if (((pos == 0) && (this.fileendpos == 0)) || (pos == this.fileendpos + 1)) {   // seek pos is append pos                this.bufstartpos = pos;                this.bufusedsize = 0;            }            this.bufendpos = this.bufstartpos + this.bufsize - 1;        }        this.curpos = pos;    }// int fillbuf()：根据bufstartpos，填充buf[]。    private int fillbuf() throws IOException {        super.seek(this.bufstartpos);        this.bufdirty = false;        return super.read(this.buf);    }}

// boolean write(byte bw, long pos)：向当前文件POS位置写入字节BW。// 根据POS的不同及BUF的位置：存在修改、追加、BUF中、BUF外等情况。在逻辑判断时，把最可能出现的情况，最先判断，这样可提高速度。// fileendpos：指示当前文件的尾偏移地址，主要考虑到追加因素    public boolean write(byte bw, long pos) throws IOException {        if ((pos >= this.bufstartpos) && (pos <= this.bufendpos)) { // write pos in buf            this.buf[(int)(pos - this.bufstartpos)] = bw;            this.bufdirty = true;            if (pos == this.fileendpos + 1) { // write pos is append pos                this.fileendpos++;                this.bufusedsize++;            }        } else { // write pos not in buf            this.seek(pos);            if ((pos >= 0) && (pos <= this.fileendpos) && (this.fileendpos != 0)) { // write pos is modify file                this.buf[(int)(pos - this.bufstartpos)] = bw;            } else if (((pos == 0) && (this.fileendpos == 0)) || (pos == this.fileendpos + 1)) { // write pos is append pos                this.buf[0] = bw;                this.fileendpos++;                this.bufusedsize = 1;            } else {                throw new IndexOutOfBoundsException();            }            this.bufdirty = true;        }        this.curpos = pos;        return true;    }

   public void seek(long pos) throws IOException {		...this.bufstartpos =  pos * bufbitlen / bufbitlen; // bufbitlen指buf[]的位长，例：若bufsize=1024，则bufbitlen=10。...}

    public boolean append(byte bw) throws IOException {        return this.write(bw, this.fileendpos + 1);    }

    public boolean write(byte bw) throws IOException {        return this.write(bw, this.curpos);    }

    public long length() throws IOException {        return this.max(this.fileendpos + 1, this.initfilelen);    }

    public long getFilePointer() throws IOException {        return this.curpos;    }

    public void write(byte b[], int off, int len) throws IOException {        long writeendpos = this.curpos + len - 1;        if (writeendpos <= this.bufendpos) { // b[] in cur bufSystem.arraycopy(b, off, this.buf, (int)(this.curpos - this.bufstartpos), len);            this.bufdirty = true;            this.bufusedsize = (int)(writeendpos - this.bufstartpos + 1);        } else { // b[] not in cur buf            super.seek(this.curpos);            super.write(b, off, len);        }        if (writeendpos > this.fileendpos)            this.fileendpos = writeendpos;        this.seek(writeendpos+1);}    public void write(byte b[]) throws IOException {        this.write(b, 0, b.length);    }

public int read(byte b[], int off, int len) throws IOException {long readendpos = this.curpos + len - 1;   if (readendpos <= this.bufendpos && readendpos <= this.fileendpos ) { // read in buf     	System.arraycopy(this.buf, (int)(this.curpos - this.bufstartpos), b, off, len);   } else { // read b[] size > buf[]   		if (readendpos > this.fileendpos) { // read b[] part in file      		len = (int)(this.length() - this.curpos + 1);       }       super.seek(this.curpos);       len = super.read(b, off, len);       readendpos = this.curpos + len - 1;   }       this.seek(readendpos + 1);       return len;}   public int read(byte b[]) throws IOException {        return this.read(b, 0, b.length);   }public void setLength(long newLength) throws IOException {        if (newLength > 0) {            this.fileendpos = newLength - 1;        } else {            this.fileendpos = 0;        }        super.setLength(newLength);}    public void close() throws IOException {        this.flushbuf();        super.close();   	}

RandomAccessFile rafi = new RandomAccessFile(SrcFile, "r");   RandomAccessFile rafo = new RandomAccessFile(DesFile, "rw");	FileChannel fci = rafi.getChannel();FileChannel fco = rafo.getChannel();	long size = fci.size();	MappedByteBuffer mbbi = fci.map(FileChannel.MapMode.READ_ONLY, 0, size);MappedByteBuffer mbbo = fco.map(FileChannel.MapMode.READ_WRITE, 0, size);long start = System.currentTimeMillis();for (int i = 0; i < size; i++) {            byte b = mbbi.get(i);            mbbo.put(i, b);}fcin.close();fcout.close();rafi.close();rafo.close();System.out.println("Spend: "+(double)(System.currentTimeMillis()-start) / 1000 + "s");