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Files and File Systems in Java
An Introduction


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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File Systems
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  • Definitions:
    • A file is a coherent collection of information that can be identified by a name
    • A file system is a method for storing and organizing files
    • A directory (or folder) is a group of files and/or directories
  • Examples:
    • MS-Windows: FAT and NTFS
    • OS X: HFS Plus
    • CD-ROM: ISO 9660
Files and Directories in Java
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  • The File and Files Classes:
    • A File object is an encapsulation of a file/directory handle (not an actual file on the file system)
    • The Files class is a utility class for operating on File and Path objects
  • Important Concepts:
    • The working directory is named "." (and it's parent is named "..")
    • Absolute (starting with a '/' in UNIX, ':' or ":\" in MS-Windows, and "\\" for UNC) and Relative Pathnames
    • The Separator Character ('/' on UNIX, '\' on MS-Windows)
    • The Path-Separator Character (':' on UNIX, ';' on MS-Windows)
  • Constructing a File Object:
    • File(java.lang.String)
    • File(java.lang.String, java.lang.String)
Operating on File Objects
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  • Checking Attributes:
    • File.canRead()
    • File.canWrite()
    • File.exists()
    • File.isDirectory()
    • File.isFile()
    • File.isHidden()
    • File.lastModified()
  • Modify Attributes:
    • File.renameTo(java.io.File)
    • File.setReadOnly()
    • File.setLastModified(long)
Operating on File Objects (cont.)
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  • Creating:
    • A directory can be created using File.mkdir()
    • A file is created by writing to it
  • Deleting:
    • File.delete()
  • Working with Directories:
    • File.list() returns a String[]
    • File.listFiles() returns a File[]
Operating on File Objects (cont.)
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An Example

javaexamples/iobasics/Dir.java
 
Operating on the File System
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  • Copying:
    • Files.copy(java.nio.file.Path, java.nio.file.Path, java.nio.file.CopyOption...)
  • Creating Links and Symbolic Links:
    • Files.createLink(java.nio.file.Path, java.nio.file.Path)
    • Files.createSymbolicLink(java.nio.file.Path, java.nio.file.Path, java.nio.file.attribute.FileAttribute...)
There's Always More to Learn
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