Input Output

• Volatile storage


  Temporary. Volatile values (stored in variables) are lost when the computer loses its power.
• Non-volatile storage


  Permanent. A Java program that is saved on a disk uses a non-volatile storage.
• Computer file


  A collection of data stored on a non-volatile device.
• Text file


  Consists of data that can be read in a text editor. Data in a text file is encoded using a scheme, such as ASCII and Unicode. Examples are program files and application files.
• Binary file


  Contains data that is not encoded as text. This file has contents in binary format, which means they cannot be understood by viewing them in a text editor.
• Main directory/root directory


  Permanent files are stored here.
• Folders/directories


  Organized stored files.
• Path


  The complete list of the disk drive plus the hierarchy of directories in which the file is located.
• Path delimiter


  The backslash (\) used to separate path components.
• Path class


  Creates objects that contain information about files and directories, such as sizes, locations, creation dates, and is used to check whether a file or directory exists.
• Files class


  Performs operations on files and directories, such as determining their attributes, creating input and output streams, and deleting them.
• import java.nio.file.*;


  Use both the Path and Files classes.
• Path filePath = Paths.get("C:\\Java\\Chapter8\\sample.txt
• Absolute path


  A complete path; it does not require any other information to locate a file on a system.
• Relative path


  Depends on other path information.
• String toString()


  Returns the String representation of the Path, eliminating double Backslashes.
• Path methods


  • getFileName(), getNameCount(), getName(int)
• Path getFileName()


  Returns the file or directory denoted by this Path; this is the last item in the sequence of name elements.
• int getNameCount()


  Returns the number of name elements in the Path.
• Path getName(int)


  Returns the name in the position of the Path specified by the integer parameter.
• toAbsolutePath()


  Convert a relative path to an absolute path.
• checkAccess()


  Verify if a file exists and if a program can access it when needed.
• delete()


  Method of the Files class accepts a Path parameter and removes the last element (file or directory) in a path or throws an exception if the deletion is unsuccessful.
• Exceptionsthrownbydelete()


  • NoSuchFileException
  • DirectoryNotEmptyException
  • SecurityException
  • IOException
• deleteIfExists()


  Method can also be used to remove a file without encountering an exception if the file does not exist.
• readAttributes()


  To retrieve useful information about a file.
• BasicFileAttributes.class


  The readAttributes() method returns an instance.
• BasicFileAttributes methods


  • size(), creationTime(), lastModifiedTime(), compareTo()
• size()


  Returns the size of the file in bytes.
• creationTime()


  Returns the date and time the file was created.
• lastModifiedTime()


  Returns the date and time the file was last edited.
• compareTo()


  Compares relationship between values retrieved from creationTime() or lastModifiedTime().
• Character


  The smallest useful piece of data and can be any letter, number, or other special symbol (such as punctuation mark) that makes up data.
• Field


  A group of characters that has some meaning. Fields are grouped together to form records.
• Record


  A collection of fields that contain data about an entity. Records are grouped to create files.
• File


  Consists of related records.
• Sequential access file


  Each record in a file is accessed one after another in the order in which it was stored, the data file is.
• Comma-separated values


  A record's fields can be organized into a single line or can be separated by a character. Values in a record that are separated by commas.
• Stream


  A flow of data.
• Input stream


  The data is taken from a source (such as a file or the keyboard) and is delivered into a program.