1. I/O Streams
A stream is a sequence of bytes that flows from a source to a destination
In a program, we read information from an input stream and write information to an output stream
A program can manage multiple streams at a time
The java.io package contains many classes that allow us to define various streams with specific characteristics

2. I/O Stream Categories
The classes in the I/O package divide input and output streams into other categories
An I/O stream is either a
character stream, which deals with text data
byte stream, which deals with byte data
An I/O stream is also either a
data stream, which acts as either a source or destination
processing stream, which alters or manages information in the stream

3. I/O class hierarchy class java.lang.Object class java.io.InputStream
class java.io.ByteArrayInputStream
class java.io.FileInputStream
class java.io.FilterInputStream
class java.io.OutputStream
class java.io.ByteArrayOutputStream
class java.io.FileOutputStream
class java.io.FilterOutputStream
class java.io.Reader
class java.io.BufferedReader …
class java.io.InputStreamReader
class java.io.Writer
class java.io.BufferedWriter
class java.io.OutputStreamWriter

4. Sources of data streams
There are three standard I/O streams:
standard input – defined by System.in
standard output – defined by System.out
standard error – defined by System.err
We use System.out when we execute println statements
System.in is declared to be a generic InputStream reference, and therefore usually must be mapped to a more useful stream with specific characteristics
FileInputStream and FileReader are classes whose constructors open a file for reading

5. Processing streams
Processing classes have constructors that take InputSteams as input and produce InputStreams with added functionality
BufferedReader, and BufferedWriter allow you to write bigger chunks of text to a stream.
Buffering is a way of combining multiple reads or writes into a single action. It is a good idea when working with text.
Examples: readLine() in BufferedReader and newLine() in BufferedWriter

6. IOExceptions
The following exception classes are defined in the java.io package:
CharConversionException
EOFException
FileNotFoundException
InterruptedIOException
InvalidClassException
InvalidObjectException
NotActiveException
NotSerializableException
ObjectStreamException
OptionalDataException
StreamCorruptedException
SyncFailedException
UnsupportedEncodingException
UTFDataFormatException
WriteAbortedException

7. Reading from a file: Listing 8.7…
StringTokenizer tokenizer;
String line, name, file="inventory.dat";
try {
FileReader fr = new FileReader (file);
BufferedReader inFile = new BufferedReader (fr);
line = inFile.readLine();
while (line != null) {
tokenizer = new StringTokenizer (line);
name = tokenizer.nextToken();
try {
units = Integer.parseInt (tokenizer.nextToken()); }
catch (NumberFormatException exception) {
System.out.println ("Error in input. Line ignored:");

8. The Keyboard Class
The Keyboard class was written by the authors of your textbook to facilitate reading data from standard input
Now we can examine the processing of the Keyboard class in more detail
The Keyboard class:
declares a useful standard input stream
handles exceptions that may be thrown
parses input lines into separate values
converts input stings into the expected type
handles conversion problems
Take a look at the code and ask questions next class