Java实现文件拷贝的4种方法
http://blog.csdn.net/ta8210/article/details/2073817
第一种方法:古老的方式
第一种方法:古老的方式
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 |
Java代码 public static long forJava(File f1,File f2) throws Exception{ long time=new Date().getTime(); int length=2097152; FileInputStream in=new FileInputStream(f1); FileOutputStream out=new FileOutputStream(f2); byte[] buffer=new byte[length]; while(true){ int ins=in.read(buffer); if(ins==-1){ in.close(); out.flush(); out.close(); return new Date().getTime()-time; }else out.write(buffer,0,ins); } } |
第2种方法:使用NIO中的管道到管道传输
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 |
Java代码 public static long forTransfer(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(); int i=0; while(true){ if(inC.position()==inC.size()){ inC.close(); outC.close(); return new Date().getTime()-time; } if((inC.size()-inC.position())<20971520) length=(int)(inC.size()-inC.position()); else length=20971520; inC.transferTo(inC.position(),length,outC); inC.position(inC.position()+length); i++; } } |
方法3:内存文件景象写(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)
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 |
Java代码 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(); } } |
第4种方法:管道对管道
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 |
Java代码 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); } } |
