package zs;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 { public byte[] getContent(String filePath) throws IOException {  File file = new File(filePath);  long fileSize = file.length();  if (fileSize > Integer.MAX_VALUE) {   System.out.println("file too big...");   return null;  }  FileInputStream fi = new
 
 FileInputStream(file);  byte[] buffer = new byte[(int) fileSize];  int offset = 0;  int numRead = 0;  while (offset < buffer.length  && (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {   offset += numRead;  }  // 確保所有資料均被讀取  if (offset != buffer.length) {  throw new IOException("Could not completely read file "
 
     + file.getName());  }  fi.close();  return buffer; } /**  * 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 可以在處理大檔案時，提升效能  *   * @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();   }  } }}