Quick Charts of I/O Classes

Quick charts of I/O classes

READER INPUT CLASSES

Arrows correspond to the stream direction which is implicit in combined constructor statements.

i.e. ← right to left for input, and left to right→ for output.

The arrows below indicate where other chained streams are likely to be attached. Check out the combined constructors.

chained sink stream ← BufferedInputStream ← chained source stream

DataInputStream dis = new DataInputStream( new BufferedInputStream( new FileInputStream( “myfile”)));

It sends to what sink?	CHARACTER STREAM INPUT CLASS	It gets from what source?	Primary Function of the Class:	Does it provide any unique methods beyond those in Reader?
CHAINABLE SINK: If chained to a sink stream, it provides a Reader stream of buffered characters to that stream. If not chained, its methods can be used return the characters. You may also want to use its readLine( ) method.	← BufferedReader ←	CHAINABLE SOURCE: Its source can be any Reader stream.	Provides buffered reading. It is usually chained to a FileReader as its source stream.	It adds the handy readLine( ) method. readLine( ) reads until encountering a \n, \r, or \r\n and then stops, returning the whole line in a String.
CHAINABLE SINK: If chained to a sink stream, it provides a Reader stream of characters from the array. If not chained, its methods can be used to return the chars from the source array.	← CharArrayReader	SOURCE NOT CHAINABLE: Its source is always an array of chars specified in its constructor	Creates a Reader stream by reading from a char array	Use the 9 methods from Reader. Adds nothing.
CHAINABLE SINK: If chained to a sink stream, it provides a Reader stream of the characters from the file. If not chained, its read(..) methods can be used to simply return the characters.	← FileReader	SOURCE NOT CHAINABLE: Its source is always a file from the file system.	Reads a file.	Use the 9 methods from Reader. Adds nothing.
CHAINABLE SINK: If chained to a sink stream, it provides a Reader stream of characters which were bytes when they came in. If not chained, its methods can be used to return values. You may simply want to use its read(..) methods.	←InputStreamReader ←	CHAINABLE SOURCE: Its source can be an InputStream stream consisting of bytes or of various other Charsets, including Unicode. It does not take a Reader stream.	Converts InputStream source bytes into a Reader stream of characters.	Use the 9 methods from Reader. It adds one getEncod-ing( ) method.
USUALLY NOT CHAINED: Because you will probably want to use its own getLineNumber(..) method.	LineNumberReader ←	CHAINABLE SOURCE: Its source can be any Reader stream	Keeps track of line numbers in a Reader stream when reading lines with readLine( ).	Use the 9 methods from Reader and especially use readLine( ) from its immediate parent BufferedReader. It adds two methods - getLineNumber( ) and setLineNumber(..).
CHAINABLE SINK: If chained to a sink stream, it provides a Reader stream of characters which emanated from the connected PipedWriter stream. If not chained, its methods return the characters from the source PipedWriter stream.	← PipedReader	SOURCE NOT CHAINABLE: Its source is always the PipedWriter stream to which it is connected.	Reads from a PipedWriter stream which has been previously written to.	Use the 9 methods from Reader. It adds one connect(.. ) method.
USUALLY NOT CHAINED: Because you will probably want to use its unread(..) pushback methods.	PushBackReader ←	CHAINABLE SOURCE: Its source can be any Reader stream	Reads from a Reader stream with the ability to put one or more chars back as if they had not been read.	Use the 9 methods from Reader. It adds three unread(..) methods for pushing characters back into the stream.
CHAINABLE SINK: If chained to a sink stream, it provides a Reader stream of characters from the String named in its constructor. If not chained, its methods return values from the source String.	← StringReader	SOURCE NOT CHAINABLE: Its source is a String specified in its constructor	Lets you apply Reader I/O stream methods to a String.	Use the 9 methods from Reader. Adds nothing.

WRITER OUTPUT CLASSES

It gets from what source?	CHARACTER STREAM OUTPUT CLASS	It sends to what sink?	Primary Function of the class:	Does it provide any unique methods beyond those in Writer?
CHAINABLE SOURCE: Its source can be any Writer stream. If not chained, its methods must be supplied with values to write.	→ BufferedWriter →	CHAINABLE SINK: Its Writer output stream can go into any other output Writer stream.	Provides buffered writing. It is usually chained to a FileWriter stream which acts as a sink.	Use the 7 methods from Writer. It adds a newLine( ) method which writes a line separator.
CHAINABLE SOURCE: Its source can be any Writer output stream. If not chained, its methods must be supplied values to write.	→ CharArrayWriter	SINK NOT CHAINABLE: The CharArrayWriter is a sink itself. Its contents are converted to a char array or String, or they can be written to another stream using writeTo( ), or, after creation, the now-filled stream object handle can be passed to a subsequent stream declaration constructor.	Allows I/O methods to be used to write an internal buffer which can later be retrieved as a char array or as a String.	Use the 7 methods from Writer. It adds five methods: size( ), writeTo( ), and reset( ), plus toCharArray( ) and toString( ) for converting the stream contents.
CHAINABLE SOURCE: Its source can be any Writer output stream. If not chained, its methods must be supplied values to write.	→ FileWriter	SINK NOT CHAINABLE: Its sink is always a file in the file system.	Writes to a file in the file system.	Use the 7 methods from Writer. Adds nothing.
CHAINABLE SOURCE: Its source can be any Writer output stream. If not chained, its methods must be supplied values to write.	→ FilterWriter →	CHAINABLE SINK: Its Writer output stream can go into any other output Writer stream sink.	Provides a convenience class to override if you want to write your own filtering.	Adds nothing to Writer's 7 methods.
CHAINABLE SOURCE: Its source can be any Writer output stream. If not chained, its methods must be supplied values to write.	→OutputStreamWriter→	CHAINABLE SINK: However its sink is always an OutputStream, for instance a FileOutputStream.	Can produce bytes as well as characters.	Use the 7 methods from Writer. It adds one getEncoding( ) method.
CHAINABLE SOURCE: Its source can be characters written to any Writer output stream. If not chained, its methods must be supplied values to write.	→ PipedWriter	SINK NOT CHAINABLE: The PipedWriter is a sink itself. Its contents are transferred automatically into the PipedReader to which it is connected.	Creates a Writer stream which is a source input to a PipedReader.
USUALLY NOT CHAINED: Because you will want to use its print(..) or println(..) methods.	PrintWriter →	CHAINABLE SINK: Its sink is always a character output stream such as a FileWriter. Or it can also go to a byte OutputStream such as a FileOutputStream.	Writes or displays Java primitives and objects as character text.	It adds 21 print( ..) and println(..) methods to the 7 methods in Writer.
CHAINABLE SOURCE: Its source can be characters from any Writer output stream. If not chained, its methods must be supplied values.	→ StringWriter	SINK NOT CHAINABLE: The StringWriter is a sink itself. Its contents are converted to a String or StringBuffer or its object handle can be passed to a subsequent stream declaration constructor.	Allows I/O methods to be used on Strings.	Use the 7 methods from Writer. It adds two methods - getBuffer( ) plus toString( ) for converting the stream contents.