读取Java文件到byte数组的三种方式

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  1. packagezs;
  3. importjava.io.BufferedInputStream;
  4. importjava.io.ByteArrayOutputStream;
  5. importjava.io.File;
  6. importjava.io.FileInputStream;
  7. importjava.io.FileNotFoundException;
  8. importjava.io.IOException;
  9. importjava.io.RandomAccessFile;
  10. importjava.nio.ByteBuffer;
  11. importjava.nio.MappedByteBuffer;
  12. importjava.nio.channels.FileChannel;
  13. importjava.nio.channels.FileChannel.MapMode;
  15. publicclassFileUtils{
  16. publicbyte[]getContent(StringfilePath)throwsIOException{
  17. Filefile=newFile(filePath);
  18. longfileSize=file.length();
  19. if(fileSize>Integer.MAX_VALUE){
  20. System.out.println("filetoobig...");
  21. returnnull;
  22. }
  23. FileInputStreamfi=newFileInputStream(file);
  24. byte[]buffer=newbyte[(int)fileSize];
  25. intoffset=0;
  26. intnumRead=0;
  27. while(offset<buffer.length
  28. &&(numRead=fi.read(buffer,offset,buffer.length-offset))>=0){
  29. offset+=numRead;
  30. }
  31. //确保所有数据均被读取
  32. if(offset!=buffer.length){
  33. thrownewIOException("Couldnotcompletelyreadfile"
  34. +file.getName());
  35. }
  36. fi.close();
  37. returnbuffer;
  38. }
  40. /**
  41. *thetraditionalioway
  42. *
  43. *@paramfilename
  44. *@return
  45. *@throwsIOException
  46. */
  47. publicstaticbyte[]toByteArray(Stringfilename)throwsIOException{
  49. Filef=newFile(filename);
  50. if(!f.exists()){
  51. thrownewFileNotFoundException(filename);
  52. }
  54. ByteArrayOutputStreambos=newByteArrayOutputStream((int)f.length());
  55. BufferedInputStreamin=null;
  56. try{
  57. in=newBufferedInputStream(newFileInputStream(f));
  58. intbuf_size=1024;
  59. byte[]buffer=newbyte[buf_size];
  60. intlen=0;
  61. while(-1!=(len=in.read(buffer,0,buf_size))){
  62. bos.write(buffer,0,len);
  63. }
  64. returnbos.toByteArray();
  65. }catch(IOExceptione){
  66. e.printStackTrace();
  67. throwe;
  68. }finally{
  69. try{
  70. in.close();
  71. }catch(IOExceptione){
  72. e.printStackTrace();
  73. }
  74. bos.close();
  75. }
  76. }
  78. /**
  79. *NIOway
  80. *
  81. *@paramfilename
  82. *@return
  83. *@throwsIOException
  84. */
  85. publicstaticbyte[]toByteArray2(Stringfilename)throwsIOException{
  87. Filef=newFile(filename);
  88. if(!f.exists()){
  89. thrownewFileNotFoundException(filename);
  90. }
  92. FileChannelchannel=null;
  93. FileInputStreamfs=null;
  94. try{
  95. fs=newFileInputStream(f);
  96. channel=fs.getChannel();
  97. ByteBufferbyteBuffer=ByteBuffer.allocate((int)channel.size());
  98. while((channel.read(byteBuffer))>0){
  99. //donothing
  100. //System.out.println("reading");
  101. }
  102. returnbyteBuffer.array();
  103. }catch(IOExceptione){
  104. e.printStackTrace();
  105. throwe;
  106. }finally{
  107. try{
  108. channel.close();
  109. }catch(IOExceptione){
  110. e.printStackTrace();
  111. }
  112. try{
  113. fs.close();
  114. }catch(IOExceptione){
  115. e.printStackTrace();
  116. }
  117. }
  118. }
  120. /**
  121. *MappedFilewayMappedByteBuffer可以在处理大文件时，提升性能
  122. *
  123. *@paramfilename
  124. *@return
  125. *@throwsIOException
  126. */
  127. publicstaticbyte[]toByteArray3(Stringfilename)throwsIOException{
  129. FileChannelfc=null;
  130. try{
  131. fc=newRandomAccessFile(filename,"r").getChannel();
  132. MappedByteBufferbyteBuffer=fc.map(MapMode.READ_ONLY,0,
  133. fc.size()).load();
  134. System.out.println(byteBuffer.isLoaded());
  135. byte[]result=newbyte[(int)fc.size()];
  136. if(byteBuffer.remaining()>0){
  137. //System.out.println("remain");
  138. byteBuffer.get(result,0,byteBuffer.remaining());
  139. }
  140. returnresult;
  141. }catch(IOExceptione){
  142. e.printStackTrace();
  143. throwe;
  144. }finally{
  145. try{
  146. fc.close();
  147. }catch(IOExceptione){
  148. e.printStackTrace();
  149. }
  150. }
  151. }
  152. }
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原文地址：https://www.cnblogs.com/xue88ming/p/7183006.html