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`java.nio.file.Files` is a utility class in the Java NIO (New I/O) package, located in the `java.nio.file` package. `java.nio.file.Files` provides a series of static methods to operate files and directories in the file system, greatly simplifying file I/O operations. ### Main Features * **Static Methods**: All methods are static, no need to create instances * **Rich Functionality**: Provides various functions such as file reading/writing, attribute operations, directory traversal * **Exception Handling**: Unified use of `IOException` for file operation exceptions * **Works with Path**: Mainly used together with the `java.nio.file.Path` interface * * * ## Common Methods Classification **Note:** Many methods throw IOException, exception handling is required when using them. Here are the commonly used methods of the java.nio.file.Files class: | Method | Description | | --- | --- | | **File Operations** | | `static Path copy(Path source, Path target, CopyOption... options)` | Copy file from source path to target path | | `static Path move(Path source, Path target, CopyOption... options)` | Move or rename file | | `static void delete(Path path)` | Delete file | | `static boolean deleteIfExists(Path path)` | Delete if file exists | | **File Attributes** | | `static boolean exists(Path path, LinkOption... options)` | Check if file exists | | `static boolean isDirectory(Path path, LinkOption... options)` | Check if path is a directory | | `static boolean isRegularFile(Path path, LinkOption... options)` | Check if path is a regular file | | `static boolean isReadable(Path path)` | Check if file is readable | | `static boolean isWritable(Path path)` | Check if file is writable | | `static boolean isExecutable(Path path)` | Check if file is executable | | `static long size(Path path)` | Return file size (in bytes) | | `static FileTime getLastModifiedTime(Path path, LinkOption... options)` | Get file last modified time | | **File Content Operations** | | `static byte[] readAllBytes(Path path)` | Read all bytes from file | | `static List readAllLines(Path path)` | Read all lines from file | | `static List readAllLines(Path path, Charset cs)` | Read all lines from file with specified charset | | `static Stream lines(Path path)` | Return stream of lines in file | | `static Stream lines(Path path, Charset cs)` | Return stream of lines in file with specified charset | | `static Path write(Path path, byte[] bytes, OpenOption... options)` | Write bytes to file | | `static Path write(Path path, Iterable lines, OpenOption... options)` | Write text lines to file | | **Directory Operations** | | `static Stream list(Path dir)` | List entries in directory | | `static DirectoryStream newDirectoryStream(Path dir)` | Open directory stream | | `static Path createDirectory(Path dir, FileAttribute... attrs)` | Create directory | | `static Path createDirectories(Path dir, FileAttribute... attrs)` | Create directory (including all non-existent parent directories) | | **Temporary Files/Directories** | | `static Path createTempFile(Path dir, String prefix, String suffix, FileAttribute... attrs)` | Create temporary file | | `static Path createTempDirectory(Path dir, String prefix, FileAttribute... attrs)` | Create temporary directory | | **Others** | | `static Path createFile(Path path, FileAttribute... attrs)` | Create new file | | `static SeekableByteChannel newByteChannel(Path path, OpenOption... options)` | Open or create file, return seekable byte channel | | `static InputStream newInputStream(Path path, OpenOption... options)` | Open file input stream | | `static OutputStream newOutputStream(Path path, OpenOption... options)` | Open file output stream | | `static BufferedReader newBufferedReader(Path path)` | Open buffered reader | | `static BufferedWriter newBufferedWriter(Path path, OpenOption... options)` | Open buffered writer | | `static String probeContentType(Path path)` | Probe file content type | ### 1. File Operations #### File Reading and Writing ## Example // Read all lines from file List lines = Files.readAllLines(path); // Write to file Files.write(path, content.getBytes()); // Append to file Files.write(path, content.getBytes(), StandardOpenOption.APPEND); #### File Copy/Move/Delete ## Example // Copy file Files.copy(sourcePath, targetPath); // Move/rename file Files.move(sourcePath, targetPath); // Delete file Files.delete(path); ### 2. Directory Operations #### Create Directory ## Example // Create single-level directory Files.createDirectory(path); // Create multi-level directory Files.createDirectories(path); #### Directory Traversal ## Example // Traverse directory try(Stream paths = Files.list(directoryPath)){ paths.forEach(System.out::println); } // Recursively traverse directory try(Stream paths = Files.walk(directoryPath)){ paths.forEach(System.out::println); } ### 3. File Attribute Operations #### Get File Attributes ## Example // Check if file exists boolean exists = Files.exists(path); // Get file size long size = Files.size(path); // Get file last modified time FileTime lastModifiedTime = Files.getLastModifiedTime(path); #### Set File Attributes ## Example // Set file last modified time Files.setLastModifiedTime(path, FileTime.fromMillis(System.currentTimeMillis())); // Set file permissions Set perms = PosixFilePermissions.fromString("rwxr-x---"); Files.setPosixFilePermissions(path, perms); * * * ## Advanced Features ### 1. File Search ## Example // Find files with specific extension try(Stream paths = Files.find( directoryPath, Integer.MAX_VALUE, (path, attrs)-> path.toString().endsWith(".txt"))){ paths.forEach(System.out::println); } ### 2. Temporary File Operations ## Example // Create temporary file Path tempFile = Files.createTempFile("prefix", ".suffix"); // Create temporary directory Path tempDir = Files.createTempDirectory("tempDir"); ### 3. File Attribute Views ## Example // Get file owner UserPrincipal owner = Files.getOwner(path); // Get file store information FileStore store = Files.getFileStore(path); * * * ## Best Practices ### 1. Exception Handling ## Example try{ Files.copy(sourcePath, targetPath, StandardCopyOption.REPLACE_EXISTING); }catch(IOException e){ System.err.println("File operation failed: "+ e.getMessage()); } ### 2. Resource Cleanup ## Example try(Stream lines = Files.lines(path)){ lines.forEach(System.out::println); }// Auto-close stream ### 3. Performance Considerations * For large files, use buffered streams (`Files.newBufferedReader`/`Files.newBufferedWriter`) * Consider using `Files.walk` instead of recursive calls for batch operations * Frequently accessed attributes can be cached * * * ## Comparison with Traditional I/O | Feature | Files Class (NIO) | Traditional I/O (java.io) | | --- | --- | --- | | Method Type | Static methods | Instance methods | | Path Representation | Uses Path interface | Uses File class | | Exception Handling | Unified use of IOException | Multiple exception types | | Richness of Functionality | Richer functionality | Basic functionality | | Symbolic Link Handling | Native support | Limited support | | File Attribute Operations | More comprehensive | Limited | Through the `Files` class, Java provides a more modern and powerful file operation API, and it is recommended to use it in new projects to replace the traditional `java.io.File` class.