File Operations in Java

File Operations in Java

1). Check if the file exists in Java

 
Path path = Paths.get("H:\\temp\\hello.pdf");

public static boolean exists(final Path path) {
		return path == null ? false : Files.exists(path);
	}
 

2). Read File bytes

  
public static byte[] read(final Path path) throws IOException {
		if (Files.exists(path)) {
			return Files.readAllBytes(path);
		} else {
			throw new IOException("Unable to find file to read " + path);
		}
	}
   

3). Move the file to other location

 
  Path src = Paths.get("H:\\temp\\hello");
  Path dest = Paths.get("H:\\temp\\bye");
  
  public static void move(final Path src, final Path dest) throws IOException {
		Files.move(src, dest, StandardCopyOption.REPLACE_EXISTING);

  }
  
   

4). Get all files in given path

 
  
  getFilesFromFolder(folder, "*");
  
  public static List<Path> getFolders(final Path folder, final String glob) {
		final List<Path> files = new ArrayList<Path>();
		if (Files.exists(folder)) {
			try (DirectoryStream<Path> stream = Files.newDirectoryStream(folder, glob)) {
				for (final Path entry : stream) {
					if (Files.isDirectory(entry)) {
						System.out.println("Util scanner found folder : " + entry.getFileName());
						files.add(entry);
					}
				}
			} catch (final IOException e) {
				System.out.println("Util scanner error during search folder "+ e);
			}
		} else {
			System.out.println("Util scanner, root does not exist " + folder);
		}
		return files;
	}
   

5). Get all files from given folder path with given file name text

 
   
  public static Map<String, List<Path>> getFilesFromFolders(final Path rootFolder, final String glob) {
		final Map<String, List<Path>> filesFromFolders = new LinkedHashMap<String, List<Path>>();
		final List<Path> folders = getFolders(rootFolder);
		for (final Path folder : folders) {
			final List<Path> files = getFilesFromFolder(folder, empty(glob) ? "*" : glob);
			if (exists(files)) {
				final String key = folder.getFileName().toString();
				filesFromFolders.put(key, new ArrayList<Path>());
				for (final Path file : files) {
					filesFromFolders.get(key).add(file);
				}
			}
		}
		return filesFromFolders;

	} 
 

6). Delete all files from given path with given extension

 
   
  public static void deleteAllWithExt(final Path folder, final String extension) throws IOException {
		if (Files.exists(folder)) {
			Files.walkFileTree(folder, new SimpleFileVisitor<Path>() {
				@Override
				public FileVisitResult postVisitDirectory(final Path arg0, final IOException arg1) throws IOException {
					return FileVisitResult.CONTINUE;
				}

				@Override
				public FileVisitResult visitFile(final Path file, final BasicFileAttributes attrs) throws IOException {
					System.out.println("Delete file " + folder);
					if (file.toString().toUpperCase().endsWith(extension.toUpperCase())) {
						Files.delete(file);
					}
					return FileVisitResult.CONTINUE;
				}
			});
		} else {
			System.out.println("Try to delete non existing directory " + folder);
		}
	}

 

7). Delete all files from given path

 
   
   public static void deleteAll(final Path folder) throws IOException {
		if (Files.exists(folder)) {
			Files.walkFileTree(folder, new SimpleFileVisitor<Path>() {
				@Override
				public FileVisitResult postVisitDirectory(final Path arg0, final IOException arg1) throws IOException {
					System.out.println("Delete folder " + folder);
					Files.delete(arg0);
					return FileVisitResult.CONTINUE;
				}

				@Override
				public FileVisitResult visitFile(final Path file, final BasicFileAttributes attrs) throws IOException {
					System.out.println("Delete file " + folder);
					Files.delete(file);
					return FileVisitResult.CONTINUE;
				}
			});
		} else {
			System.out.println("Try to delete non existing directory " + folder);
		}
	}
 

8). How to get the type of a file in java?

9). Rename file to new Name

 
  
   	public static void renameToNewfile(File srcFile,String localFolderName)
			throws IOException {
		String currentVersion =  localFolderName+File.separator+srcFile.getName();
		boolean renamed = srcFile.renameTo(new File(currentVersion));
		System.out.println(srcFile.getName() + " renamed to -> " + renamed);
	}

 

10). Rename all files in given folder

 
    
   public static void renameLocalFilesInDir(String localFolderName) throws Exception {
		//renameLocalFilesInDir("H:\\temp\\hello");
		File srcDir = new File(localFolderName);
		File backup = new File(srcDir.getAbsolutePath()+File.separator+"backup");
		backup.mkdir();
		
		for (File srcFile : srcDir.listFiles()) {
			if (srcFile.isDirectory()) {
				recursiveFilesRename(srcFile.listFiles(), 0,backup.getAbsolutePath());
			} else {
				renameToNewfile(srcFile,backup.getAbsolutePath());
			}
		}
	}

	public static void recursiveFilesRename(File[] fileArray, int level,
			String localFolderName) throws Exception {
		for (File srcFile : fileArray) {
			if (srcFile.isFile()) {
				renameToNewfile(srcFile,localFolderName);
			} else if (srcFile.isDirectory()) {
				recursiveFilesRename(srcFile.listFiles(), level + 1,
						localFolderName);
			}

		}
	}
 

11). Replace text inside file in java

How to read data from a file in java?

 
   
  	public static void replace(final Path path, final String regex, final String text) throws IOException {
		String file = new String(Files.readAllBytes(Paths.get("file.txt")));
		file = file.replaceAll(regex, text);
		Files.write(path, file.getBytes());
	}
  
 

12). How to read a file and write to another file in java?

 
   
  	public static void readWriteInFile() throws IOException {
         
		String fileText = new String(Files.readAllBytes(Paths.get(""H:\\temp\\file.txt")));
        Path path = Paths.get("H:\\temp\\hello.txt");
        
		Files.write(path, fileText.getBytes());
	}
  
 

13). How to write a string to a file in java?

 
   
  	public static void  writeStringInFile() throws IOException {
         
		String textString ="Hello World!!!";
        Path path = Paths.get("H:\\temp\\hello.txt");
        
		Files.write(path, textString.getBytes());
	}
  
 

In this article, we have seen File Operations in Java