File Input Output

File Input Output
Files come in two types in Java

Binary

processed as a sequence of bytes
file format is the same as memory and machine specific
Java binary files are platform independent (as of 1.2)

Text

processed as a sequence of characters (a string)
ASCII code
portable
utilizes "\n" and "\eof"

I/O in Java

Handled by streams. A stream is an object that pipes information to or from another object. Two streams you are probably familiar with are System.out and System.in. Each of these pipe information to/from the standard I/O device (screen/keyboard).

Java abstract classes InputStream and OutputStream serve as the root class for reading and writing binary data. To process string data and primitive types, one uses subclasses DataInputStream and DataOutputStream.

Java abstract classes Reader and Writer are the root classes for text file I/O

Specialized subclasses

There are numerous subclasses available for specialized I/O operations.

binary I/O

FileInputStream
FileOutputStream

printing primitives

PrintStream (deprecated by JDK 1.2)
PrintWriter

provides Java international I/O

text I/O

FileReader // another subclass BufferedReader places the entire file into a large area of memory adding even more flexibility to the data manipulation
FileWriter

Reading Data

Connect an input stream to the file

Read the data

Close the file

Example Java™ API

import java.io;

File fileName = new File (testFile.txt); // a file object could be created with a GUI as in TextIO.java

BufferedReader br //br is the pipe between the file object and memory object
= new BufferedReader(new FileReader(fileName));

String line = br.readLine(); // reading in a single line of text into the String object line
// BufferedReader.readLine() returns null when \eof is reached

br.close();