midterm

• Exception


  An event that occurs during the execution of a program that disrupts the normal flow of instructions
• Exception handling


  The process used to change the normal flow of code execution if a specified exception occurs
• Checked exceptions

  • ClassNotFoundException
  • IllegalAccessException
  • InstantiationException
  • NoSuchMethodException
• Unchecked exceptions (runtime exceptions)

  • ArithmeticException
  • ArrayIndexOutOfBoundsException
  • ArrayStoreException
  • InputMismatchException
  • NullPointerException
  • NumberFormatException
  • StringIndexOutOfBoundsException
• try block


  A block of code that might throw an exception that can be handled by a matching catch block
• catch block


  A segment of code that can handle an exception that might be thrown by the try block that precedes it
• getMessage()


  Method to determine Java's message about the exception
• Only one (1) try block is accepted in a program but there can be multiple catch blocks
• User-defined exception


  Created by extending the Exception class
• finally block


  Contains statements which are executed whether or not an exception is thrown
• There can only be one (1) finally block after a try-catch structure but it is not required
• throw statement


  Sends an exception out of a block or a method so it can be handled elsewhere
• Volatile storage


  Temporary storage, values stored in variables are lost when the computer loses power
• Non-volatile storage


  Permanent storage, a Java program that is saved on a disk uses non-volatile storage
• Types of files

  • Text file
  • Binary file
• The common characteristics of a text file and binary file are size, name, and date and time of creation
• Path


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

  • toString()
  • getFileName()
  • getNameCount()
  • getName(int)
• Converting a relative path to an absolute path

  Use the toAbsolutePath() method
• checkAccess()


  Method to verify if a file exists and if a program can access it when needed
• Arguments of the checkAccess() method

  • None
  • READ
  • WRITE
  • EXECUTE
• delete()


  Method to remove the last element (file or directory) in a path
• Exceptions thrown by delete()

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


  Method to remove a file without encountering an exception if the file does not exist
• readAttributes()


  Method to retrieve useful information about a file
• BasicFileAttributes methods

  • size()
  • creationTime()
  • lastModifiedTime()
  • compareTo()
• Character


  The smallest useful piece of data, can be a letter, number, or special symbol
• Field


  A group of characters that has some meaning
• Record


  A collection of fields that contain data about an entity
• File


  A collection of related records
• Sequential access file


  A file where each record is accessed one after another in the order in which it was stored
• Comma-separated values


  Values in a record that are separated by commas
• Stream


  A flow of data, input stream is from a source to a program, output stream is from a program to a destination
• Buffer


  A memory location into which you can write data, which you can read again later
• Flushing


  Clears any bytes that have been sent to a buffer for output but have not yet been displayed on a hardware device
• Input and Output Classes

  • InputStream
  • FileInputStream
  • BufferedInputStream
  • OutputStream
  • FileOutputStream
  • BufferedOutputStream
  • PrintStream
  • Reader
  • BufferedReader
  • BufferedWriter
• Common OutputStream methods

  • close()
  • flush()
  • write(byte[] b)
  • write(byte[] b, int off, int len)
• newOutputStream()


  Method to create a writeable file