java读取文件

  1 java8读取文本文件

  2 

  3         

  4     public static void java8ReadFileLines(String fileName) throws IOException {

  5         List lineList = Files.readAllLines(Paths.get(fileName), StandardCharsets.UTF_8);

  6 

  7         for(String line:lineList){

  8             System.out.println(line);

  9         }

 10     }    

 11     

 12         

 13         

 14 一行一行地读取文件

 15 

 16 

 17     public static void readFileByLines(String fileName) {

 18         File file = new File(fileName);

 19         BufferedReader reader = null;

 20         try {

 21             reader = new BufferedReader(new FileReader(file));

 22             String line = null;

 23             while((line=reader.readLine())!=null ) {

 24                 System.out.println(line);

 25             }

 26         }catch (IOException e) {

 27 

 28         }finally {

 29             if(reader!=null) {

 30                 try{

 31                     reader.close();

 32                 }catch (IOException e) {

 33                     ;

 34                 }

 35             }

 36         }

 37     }    

 38     

 39     

 40     

 41 一次读取多个字符

 42 

 43 

 44     public static void readFileByMultiChars(String fileName) {

 45         File file = new File(fileName);

 46         try{

 47             InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream(file));

 48 

 49             char[] tempChars = new char[30];

 50 

 51             int readCount = 0;

 52             while((readCount=inputStreamReader.read(tempChars))!=-1) {

 53                 if(readCount==tempChars.length) {

 54                     System.out.println(tempChars);

 55                 }else{

 56                     System.out.println(Arrays.copyOf(tempChars, readCount));

 57                 }

 58             }

 59 

 60 

 61             inputStreamReader.close();

 62         }catch(Exception e) {

 63             e.printStackTrace();

 64         }

 65     }    

 66 

 67 

 68         

 69 一个字符一个字符地读取

 70 

 71 

 72     public static void readFileByChars(String fileName) {

 73         File file = new File(fileName);

 74         try{

 75             InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream(file));

 76 

 77             int tempChar;

 78 

 79             while((tempChar=inputStreamReader.read())!=-1) {

 80                 System.out.println((char)tempChar);

 81             }

 82 

 83 

 84             inputStreamReader.close();

 85         }catch(Exception e) {

 86             e.printStackTrace();

 87         }

 88     }        

 89 

 90 

 91         

 92 java8读取字节 超级简单

 93 

 94 

 95     public static byte[] java8ReadBytes(String fileName) throws IOException {

 96         return Files.readAllBytes(Paths.get(fileName));

 97     }

 98 

 99 

100 

101 一个字节一个字节地读取

102 

103 

104    public static void readFileByOneByte(String fileName) {

105         File file = new File(fileName);

106         InputStream inputStream = null;

107 

108         try{

109             inputStream = new FileInputStream(file);

110             int tempByte;

111             while( (tempByte=inputStream.read())!=-1) {

112                 System.out.println(tempByte);

113             }

114 

115             inputStream.close();

116         }catch (IOException e) {

117             System.out.println(e);

118         }

119 

120     }

121     

122     

123  

124 一个字节一个字节读取到ByteBuffer

125 

126 

127     public static byte[] readFileByOneByteToBuffer(String fileName) {

128 

129 

130         ByteBuffer byteBuffer = ByteBuffer.allocate(1024 * 1024);

131 

132         File file = new File(fileName);

133         InputStream inputStream = null;

134 

135         try{

136             inputStream = new FileInputStream(file);

137             int tempByte;

138             while( (tempByte=inputStream.read())!=-1) {

139                 byteBuffer.put((byte)tempByte);

140             }

141 

142             inputStream.close();

143         }catch (IOException e) {

144             System.out.println(e);

145         }

146 

147         byteBuffer.flip();

148         System.out.println("one limit:" + byteBuffer.limit());

149         byte[] result = new byte[byteBuffer.limit()];

150         byteBuffer.get(result);

151 

152         return result;

153 

154 

155     }

156     

157     

158     

159 多个字节进行读取

160 

161 

162     public static void readFileByMultiBytes(String fileName) {

163 

164         File file = new File(fileName);

165         InputStream inputStream = null;

166 

167         try {

168             byte[] bytes = new byte[50];

169             int byteRead = 0;

170             inputStream = new FileInputStream(fileName);

171 

172             while( (byteRead = inputStream.read(bytes))!=-1 ) {

173                 System.out.println(byteRead);

174             }

175         }catch(IOException e) {

176             System.out.println(e);

177         }finally {

178             if(inputStream!=null) {

179                 try{

180                     inputStream.close();

181                 }catch(IOException e){

182                     System.out.println("iput stream close exception" +  e);

183                 }

184             }

185         }

186     }

187     

188     

189   

190 读取多个字节到ByteBuffer

191 

192 

193     public static byte[] readFileByMultiBytesToBuffer(String fileName) {

194 

195         ByteBuffer byteBuffer = ByteBuffer.allocate(1024*1024);

196         InputStream inputStream = null;

197 

198         try {

199             byte[] bytes = new byte[50];

200             int byteRead = 0;

201             inputStream = new FileInputStream(fileName);

202 

203             int count = 0;

204             while( (byteRead = inputStream.read(bytes))!=-1 ) {

205                 byteBuffer.put(bytes, 0, byteRead);

206                 count+=byteRead;

207             }

208 

209             System.out.println("readCount:"+count);

210         }catch(IOException e) {

211             System.out.println(e);

212         }finally {

213             if(inputStream!=null) {

214                 try{

215                     inputStream.close();

216                 }catch(IOException e){

217                     System.out.println("iput stream close exception" +  e);

218                 }

219             }

220         }

221 

222         byteBuffer.flip();

223         System.out.println("multi limit:" + byteBuffer.limit());

224         byte[] result = new byte[byteBuffer.limit()];

225         byteBuffer.get(result);

226 

227         return result;

228     }            

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