src/main/java/eu/svjatoslav/commons/file/IOHelper.java

   1 /*
   2  * Svjatoslav Commons - shared library of common functionality.
   3  * Copyright ©2012-2014, Svjatoslav Agejenko, svjatoslav@svjatoslav.eu
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of version 3 of the GNU Lesser General Public License
   7  * or later as published by the Free Software Foundation.
   8  */
   9
  10 package eu.svjatoslav.commons.file;
  11
  12 import java.io.File;
  13 import java.io.FileInputStream;
  14 import java.io.FileNotFoundException;
  15 import java.io.FileOutputStream;
  16 import java.io.IOException;
  17 import java.io.UnsupportedEncodingException;
  18
  19 public class IOHelper {
  20
  21         /**
  22          * Deletes files and directories recursively. WARNING!!! Follows symlinks!!!
  23          */
  24         public static void deleteRecursively(final File file) throws IOException {
  25                 if (file.isDirectory()) {
  26
  27                         for (final File subFile : file.listFiles())
  28                                 deleteRecursively(subFile);
  29
  30                         if (!file.delete())
  31                                 throw new FileNotFoundException("Failed to delete directory: "
  32                                                 + file);
  33
  34                         return;
  35                 }
  36
  37                 if (file.isFile())
  38                         if (!file.delete())
  39                                 throw new FileNotFoundException("Failed to delete file: "
  40                                                 + file);
  41         }
  42
  43         public static byte[] getFileContents(final File file)
  44                         throws FileNotFoundException, IOException {
  45
  46                 final byte[] result = new byte[(int) file.length()];
  47                 final FileInputStream fileInputStream = new FileInputStream(file);
  48                 fileInputStream.read(result);
  49                 fileInputStream.close();
  50                 return result;
  51         }
  52
  53         public static String getFileContentsAsString(final File file)
  54                         throws FileNotFoundException, IOException {
  55                 try {
  56                         return new String(getFileContents(file), "UTF-8");
  57                 } catch (final UnsupportedEncodingException exception) {
  58                         throw new RuntimeException(exception);
  59                 }
  60         }
  61
  62         /**
  63          * Compares new file content with old file content. If content in equal,
  64          * then leaves file as-is. If content differs, then overrides file with the
  65          * new content.
  66          *
  67          * @return <code>true</code> if file was overwritten.
  68          */
  69         public static boolean overwriteFileIfContentDiffers(final File file,
  70                         final byte[] newContent) throws FileNotFoundException, IOException {
  71
  72                 checkForEquality: {
  73                         if (file.length() == newContent.length) {
  74
  75                                 final byte[] oldContent = getFileContents(file);
  76
  77                                 for (int i = 0; i < newContent.length; i++)
  78                                         if (newContent[i] != oldContent[i])
  79                                                 break checkForEquality;
  80
  81                                 // new file content in identical to old content
  82                                 return false;
  83                         }
  84                 }
  85
  86                 // New content differs from existing. Overwrite file.
  87                 saveToFile(file, newContent);
  88                 return true;
  89         }
  90
  91         public static void saveToFile(final File file, final byte[] content)
  92                         throws IOException {
  93                 final FileOutputStream fos = new FileOutputStream(file);
  94                 fos.write(content);
  95                 fos.close();
  96         }
  97
  98 }