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  • 读取Java文件到byte数组的三种方式

    [java]view plaincopy在CODE上查看代码片派生到我的代码片
     
    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
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