File class in Java

1. File class in Java

2. File class • Class File provides information about • Files and directories • The class provides • A constructor with a String argument • Specifying the name of a file or directory • The name can be either an absolute path or a relative path

3. Methods of the File class

4. Methods of the File class (cont’d)

5. FileFilter interface • FileFilter • Used for filtering the set of files shown to the user • Method • boolean accept(File pathName) • Tests whether or not the file is acceptable • Used in conjunction with • File[] listFiles method of the File class • To list files satisfying a given filter

6. NIO package • File information can also be retrieved using • Classes of the sub-packages of the java.nio package • In particular, the following classes can be used: • Path • Objects represent the location of a file or directory • Paths • provides static methods used to create a Path object • Files • provides static methods for common file and directory manipulations • DirectoryStream • enables a program to list the content of a directory

7. Path class • Path is • a programmatic representation of a path in file system • used to examine, locate, and manipulate files • composed of methods that can among other things • obtain information about path through getFileName() • compare two paths using the equals() method • instantiated by means of the get method of the Paths class • Example: Path p = Paths.get(“sample.txt”);

8. Files class • Files • provides support for common file and directory manipulations • exists(Path) • Verifies existence of a file or a directory • isReadable(Path), isWritable(Path), isExecutable(Path) • Checks file accessibility • isSameFile(Path, Path) • Checks whether two paths locate the same file • delete(Path) and deleteIfExists(Path) • Delete files or directories • copy(Path, Path)and move(Path, Path) • Copy and move files or directories

9. Files class (cont’d) • Files • allows for management of meta-data • size(Path) • size of specified file in bytes • isDirectory(Path) • returns true if specified path is a directory • getLastModifiedTime(Path) • File’s last modified time • getOwner(Path) • Owner of specified file • readAttributes(Path, Class) • Reads attributes of a file in one bulk operation

10. Basic File Attributes (Example) Path file = ...; BasicFileAttributesattr = Files.readAttributes(file, BasicFileAttributes.class); System.out.println("creationTime: " + attr.creationTime()); System.out.println("lastAccessTime: " + attr.lastAccessTime()); System.out.println("lastModifiedTime: " + attr.lastModifiedTime()); System.out.println("isDirectory: " + attr.isDirectory()); System.out.println("size: " + attr.size());

11. Reading, writing and creating files using Files class • Buffered I/O methods for text files in Files class • newBufferedReader(Path, Charset) • opens a file for reading returning a BufferedReader • Example: Charset charset = Charset.forName(“US-ASCII”); BufferedReader reader = Files.newBufferedReader(file, charset); • newBufferedWriter(Path, Charset) • returns a BufferedWriter • Example: Charset charset = Charset.forName(“US-ASCII”); BufferedWriter writer = Files.newBufferedWriter(file, charset);

12. Reading, writing and creating files using Files class (cont’d) • Unbuffered I/O methods for text files in Files class • newInputStream(Path, OpenOption...) • returns an InputStreamfor reading bytes from file • Example: InputStream in = Files.newInputStream(file); • newOutputStream(Path, Charset) • returns a OutputStream • Example: OutputStream out = Files.newOutputStream(file);