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import java.io.BufferedInputStream; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.ByteBuffer; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.nio.channels.FileChannel.MapMode; public class FileUtils { /** * the traditional io way * @param filename * @return * @throws IOException */ public static byte[] toByteArray(String filename) throws IOException{ File f = new File(filename); if(!f.exists()){ throw new FileNotFoundException(filename); } ByteArrayOutputStream bos = new ByteArrayOutputStream((int)f.length()); BufferedInputStream in = null; try{ in = new BufferedInputStream(new FileInputStream(f)); int buf_size = 1024; byte[] buffer = new byte[buf_size]; int len = 0; while(-1 != (len = in.read(buffer,0,buf_size))){ bos.write(buffer,0,len); } return bos.toByteArray(); }catch (IOException e) { e.printStackTrace(); throw e; }finally{ try{ in.close(); }catch (IOException e) { e.printStackTrace(); } bos.close(); } } /** * NIO way * @param filename * @return * @throws IOException */ public static byte[] toByteArray2(String filename)throws IOException{ File f = new File(filename); if(!f.exists()){ throw new FileNotFoundException(filename); } FileChannel channel = null; FileInputStream fs = null; try{ fs = new FileInputStream(f); channel = fs.getChannel(); ByteBuffer byteBuffer = ByteBuffer.allocate((int)channel.size()); while((channel.read(byteBuffer)) > 0){ // do nothing // System.out.println("reading"); } return byteBuffer.array(); }catch (IOException e) { e.printStackTrace(); throw e; }finally{ try{ channel.close(); }catch (IOException e) { e.printStackTrace(); } try{ fs.close(); }catch (IOException e) { e.printStackTrace(); } } } /** * Mapped File way * MappedByteBuffer 可以在处理大文件时，提升性能 * @param filename * @return * @throws IOException */ public static byte[] toByteArray3(String filename)throws IOException{ FileChannel fc = null; try{ fc = new RandomAccessFile(filename,"r").getChannel(); MappedByteBuffer byteBuffer = fc.map(MapMode.READ_ONLY, 0, fc.size()).load(); System.out.println(byteBuffer.isLoaded()); byte[] result = new byte[(int)fc.size()]; if (byteBuffer.remaining() > 0) { // System.out.println("remain"); byteBuffer.get(result, 0, byteBuffer.remaining()); } return result; }catch (IOException e) { e.printStackTrace(); throw e; }finally{ try{ fc.close(); }catch (IOException e) { e.printStackTrace(); } } } } |