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EX2: WK8 Object Oriented Programming

Terms in this set (25)

Volatile storage
- Computer memory or random access memory (RAM) - Temporary
Nonvolatile storage
- Not lost when computer loses power - Permanent
Computer file
- Collection of information stored on nonvolatile device in computer system
Permanent storage devices
- Hard disks - Zip disks - USB drives - Reels or cassettes of magnetic tape - Compact discs
Categories of files by the way they store data
- Text files
- Binary files
Data files
Contain facts and figures
Program files or application files
- Store software instructions
Path
- A complete list of disk drive plus the hierarchy of directories in which a file resides
Path class
- Use it to createobjects that contain information about files or directories, such as their locations, sizes, creation dates and whether they even exist
Files class
- Use it to perform operations on files and directories, such as deleting them, determining their attributes, and creating input and output streams
java.nio.file package
- Include it to use both the Path and Files classes - import java.nio.file.*; - nio stands for new input/output
String toString()
Returns the String representation of the Path, eliminating double backslashes
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
Deleting a Path
The Files class delete() method accepts a Path parameter and deletes the last element (file or directory) in a path or throws an exception if the deletion fails. • If you try and delete a file that does not exist, a NoSuchFileException is thrown • A directory cannot be deleted unless it is empty. If you try to delete a directory that contains files, a DirectoryNotEmptyException is thrown • If you try to delete a file but you don't have a permission, a SecurityException is thrown
Businesses store data in hierarchy
- Character
- Field
- Record
- Files
Sequential access file
- Each record is stored in order based on value in some field
Open a file
- Create object - Associate a stream of bytes with it
Close the file
- Make it no longer available to your application - You should always X you open
Stream
is an object, with data and methods (pipeline or channel) - Bytes flow into your program from an input device - Bytes flow out of your application to an output device - Most streams flow in only one direction - methods allow you to open, close, read, write
Buffer
- Memory location where bytes are held after they are logically output, but before they are sent to the output device - Using a X improves program performance as input and output operations are usually the slowest in any computerized system because of limitations imposed by the hardware.
Flushing
- Clears any bytes that have been sent to a buffer for output, but have not yet been output to a hardware device
Writing to a File
Assign file to the OutputStream - Construct a BufferedOutputStream object - Assign it to the OutputStream ■ Create a writeable file by using the Path class newOutputStream() method - Creates a file if it does not already exist - Opens the file for writing and returns an OutputStream that can be used to write bytes to the file
BufferedWriter class
- Counterpart to BufferedReader
- Writes text to an output stream, buffering the characters
- The class has three overloaded write() methods that provide for efficient writing of characters, arrays, and strings, respectively
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