【DataStructure】A useful util class for reading and writing files

Faced with the upcoming exam, Some useful methods referred to file operation drew tremenous attention. Now I make a summary to reading file.

[java] view
plaincopy

  1. import java.io.BufferedReader;
  2. import java.io.BufferedWriter;
  3. import java.io.File;
  4. import java.io.FileInputStream;
  5. import java.io.FileNotFoundException;
  6. import java.io.FileOutputStream;
  7. import java.io.IOException;
  8. import java.io.InputStreamReader;
  9. import java.io.OutputStreamWriter;
  10. import java.util.ArrayList;
  11. import java.util.HashMap;
  12. import java.util.List;
  13. import java.util.Map;
  14. public class FileUtil
  15. {
  16. public static final String SEP = "：";
  17. public static final String ENCODING = "UTF-8";
  18. /**
  19. * Read the content from file, the format of content is like "Key：Value"
  20. * TODO
  21. *
  22. * @time Jul 17, 2014 11:21:50 AM
  23. * @param filePath
  24. * @return
  25. * @throws Exception
  26. * @return Map<String,String>
  27. */
  28. public static Map<String, String> readFileToMap(String filePath)
  29. throws Exception
  30. {
  31. System.out.println("读文件[" + filePath + "]开始...");
  32. Map<String, String> contents = new HashMap<String, String>();
  33. File file = new File(filePath);
  34. BufferedReader reader = null;
  35. try
  36. {
  37. reader = new BufferedReader(new InputStreamReader(
  38. new FileInputStream(file), ENCODING));
  39. String info = null;
  40. while ((info = reader.readLine()) != null)
  41. {
  42. contents.put(info.split(SEP)[0], info.split(SEP)[1]);
  43. }
  44. }
  45. catch (FileNotFoundException e)
  46. {
  47. System.out.println("文件[" + filePath + "]未找到.");
  48. throw e;
  49. }
  50. catch (IOException e)
  51. {
  52. System.out.println("文件IO操作出错, 异常信息: " + e.getMessage());
  53. throw e;
  54. }
  55. catch (Exception e)
  56. {
  57. System.out.println("读文件出错, 异常信息: " + e.getMessage());
  58. throw e;
  59. }
  60. finally
  61. {
  62. if (reader != null)
  63. {
  64. try
  65. {
  66. reader.close();
  67. }
  68. catch (IOException e)
  69. {
  70. System.out.println("关闭IO流出错, 异常信息: " + e.getMessage());
  71. throw e;
  72. }
  73. }
  74. }
  75. System.out.println("读文件[" + filePath + "]结束.");
  76. return contents;
  77. }
  78. /**
  79. * Read the content from file, every line will be an element of list.
  80. *
  81. * @time Jul 17, 2014 11:39:07 AM
  82. * @param fileName
  83. * @return
  84. * @return List<String>
  85. */
  86. public static List<String> readFileToList(String fileName) throws Exception
  87. {
  88. List<String> infos = new ArrayList<String>();
  89. BufferedReader reader = null;
  90. try
  91. {
  92. reader = new BufferedReader(new InputStreamReader(
  93. new FileInputStream(new File(fileName)), "utf-8"));
  94. String info = null;
  95. while ((info = reader.readLine()) != null)
  96. {
  97. infos.add(info);
  98. }
  99. }
  100. catch (FileNotFoundException e)
  101. {
  102. System.out.println("文件[" + fileName + "]未找到.");
  103. throw e;
  104. }
  105. catch (IOException e)
  106. {
  107. System.out.println("文件IO操作出错, 异常信息: " + e.getMessage());
  108. throw e;
  109. }
  110. finally
  111. {
  112. try
  113. {
  114. if (reader != null)
  115. {
  116. reader.close();
  117. }
  118. }
  119. catch (IOException e)
  120. {
  121. e.printStackTrace();
  122. }
  123. }
  124. return infos;
  125. }
  126. /**
  127. * Read all the content from filePath at a time.
  128. *
  129. * @time Jul 17, 2014 11:45:55 AM
  130. * @param filePathOrFileName
  131. * @return
  132. * @return String
  133. */
  134. public static String readFileToString(String filePath) throws Exception
  135. {
  136. InputStreamReader isReder = null;
  137. BufferedReader br = null;
  138. StringBuffer sb = new StringBuffer();
  139. try
  140. {
  141. File f = new File(filePath);
  142. if (f.isFile() && f.exists())
  143. {
  144. isReder = new InputStreamReader(new FileInputStream(f), "UTF-8");
  145. br = new BufferedReader(isReder);
  146. String line;
  147. while ((line = br.readLine()) != null)
  148. {
  149. sb.append(line).append("\r\n");
  150. }
  151. }
  152. }
  153. catch (Exception e)
  154. {
  155. System.out.println("exception when reading the file" + filePath);
  156. throw e;
  157. }
  158. finally
  159. {
  160. if (isReder != null)
  161. {
  162. try
  163. {
  164. isReder.close();
  165. }
  166. catch (IOException e)
  167. {
  168. e.getMessage();
  169. }
  170. }
  171. if (br != null)
  172. {
  173. try
  174. {
  175. br.close();
  176. }
  177. catch (IOException e)
  178. {
  179. e.getMessage();
  180. }
  181. }
  182. }
  183. return sb.toString();
  184. }
  185. /**
  186. * Write result to the fileName
  187. *
  188. * @time Jul 17, 2014 4:57:57 PM
  189. * @param result
  190. * @param fileName
  191. * @return void
  192. */
  193. public static void writeFile(String result, String fileName)
  194. {
  195. File f = new File(fileName);
  196. OutputStreamWriter osw = null;
  197. BufferedWriter bw = null;
  198. try
  199. {
  200. if (!f.exists())
  201. {
  202. f.createNewFile();
  203. }
  204. osw = new OutputStreamWriter(new FileOutputStream(f), "UTF-8"); //"gbk"
  205. bw = new BufferedWriter(osw);
  206. bw.write(result);
  207. }
  208. catch (IOException e)
  209. {
  210. System.out.println("IOException when writing result, "
  211. + e.getMessage());
  212. }
  213. catch (Exception e)
  214. {
  215. System.out.println("Exception when writing result, "
  216. + e.getMessage());
  217. }
  218. finally
  219. {
  220. if (bw != null)
  221. {
  222. try
  223. {
  224. bw.close();
  225. }
  226. catch (IOException e)
  227. {
  228. System.out.println("IOException when closing FileWriter, "
  229. + e.getMessage());
  230. }
  231. }
  232. if (osw != null)
  233. {
  234. try
  235. {
  236. osw.close();
  237. }
  238. catch (IOException e)
  239. {
  240. System.out.println("IOException when closing bufferwriter, "
  241. + e.getMessage());
  242. }
  243. }
  244. }
  245. }
  246. public static void main(String[] args) throws Exception
  247. {
  248. Map<String, String> testMap = FileUtil.readFileToMap("input.txt");
  249. System.out.println("---------------------");
  250. for (Map.Entry<String, String> entry : testMap.entrySet())
  251. {
  252. System.out.println(entry.getKey() + ":" + entry.getValue());
  253. }
  254. System.out.println("---------------------");
  255. List<String> testList = FileUtil.readFileToList("input.txt");
  256. for (String str : testList)
  257. {
  258. System.out.println(str);
  259. }
  260. System.out.println("---------------------");
  261. String test = FileUtil.readFileToString("input.txt");
  262. FileUtil.writeFile(test, "output.txt");
  263. }
  264. }

【DataStructure】A useful util class for reading and writing files,布布扣,bubuko.com

时间： 2024-10-12 07:55:09

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