Java I/O Character Streams

In this section we will discuss the I/O Character Streams.

Character streams works with the characters rather than the byte. In Java characters are stored by following the Unicode (allows a unique number for every character) conventions. In such kind of storage characters becomes the platform independent, program independent, language independent. Characters storage using Unicode convention makes the Java ready for internationalization and for this Java provides the Character stream I/O. Character stream I/O is helpful for internationalization because it automatically translated the internal format to and from the local character set.

In Java to facilitate the character stream I/O the character stream classes are defined. These classes are drawn from the Reader and Writer classes. Both of these classes are abstract classes. where the Reader class is used for input (read from) and the Writer class is used for output (write to). To work with the file I/O specialized classes are the FileReader and FileWriter.

Reader : An abstract class that facilitate to take input (read) the character stream. Subclasses of this class must have to implement the read(char[], int, int) and close() methods.

public abstract class Reader extends Object implements Readable, Closeable

Method Description

close() : This method is used to close the resource and the resource associated to the stream get released.

public abstract void close() throws IOException
mark(int readAheadLimit) : This method is used to mark the current position in the stream. This method operation is not supported by the all character-input stream.

public void mark(int readAheadLimit) throws IOException
markSupported() : This method specifies that whether the mark() operation is supported by the stream or not. Default value is false.

public boolean markSupported()
read() : This method is used to read the characters. It reads a single character. It returns the number of read characters in the range 0 to 65535 or -1 if it reaches the end of the stream.

public int read() throws IOException
read(char[] cbuf) : This method is used to read the characters. Characters are read into an array. This method returns the number of read characters or -1 if it reaches the end of stream.

public int read(char[] cbuf) throws IOException
read(char[] cbuf, int off, int len) : This method is used to read the characters. Characters are read into an array at specified len.

public abstract int read(char[] cbuf, int off, int len) throws IOException
read(CharBuffer target) : This method is used to read characters from the specified character buffer.

public int read(CharBuffer target) throws IOException
ready() : This method specifies that is the stream ready for reading or not.

public boolean ready() throws IOException
reset() : This method repositioned the stream where(if) the mark method was marked the current position in the input stream. Or reset according to the particular stream.

public void reset() throws IOException
skip(long n) : This method is used to skipped over the characters in the stream.

public long skip(long n) throws IOException

Some subclasses of the Reader class are given into table :

Classes	Description
BufferedReader	BufferedReader class provides the facility to read texts from a character-input stream using buffer.
CharArrayReader	CharArrayReader implements the character buffer to read character stream.
FilterReader	This class is used for reading the filtered character streams.
InputStreamReader	This class acts as a bridge from byte streams to character streams.
PipedReader	Piped character input stream
StringReader	Character stream read from the String

Writer : An abstract class that facilitate to write character streams. Subclasses of this class must have to implement the write(char[], int, int), flush() and close() methods.

public abstract class Writer extends Object implements Appendable, Closeable, Flushable

Method Description

append(char c) : This method adds the specified character at the end to the stream.

public Writer append(char c) throws IOException
append(CharSequence csq) : This method adds the specified character sequence at the end to the writer stream.

public Writer append(CharSequence csq) throws IOException
append(CharSequence csq, int start, int end) : This method is used to add the character to the writer stream in the subsequence of the character sequence.

public Writer append(CharSequence csq, int start, int end) throws IOException
close() : This method is used to close the writer stream.

public abstract void close() throws IOException
flush() : This method is used to flush the writer stream.

public abstract void flush() throws IOException
write(char[] cbuf) : This method is used to write the array of characters.

public void write(char[] cbuf) throws IOException
write(char[] cbuf, int off, int len) : This method is used to write the specified portion of an Array of characters.

public abstract void write(char[] cbuf, int off, int len) throws IOException
write(int c) : This method is used to write a single character.

public void write(int c) throws IOException
write(String str) : This method is used to write a string.

public void write(String str) throws IOException
write(String str, int off, int len) : This method is used to write the specified portion of string.

public void write(String str, int off, int len) throws IOException

Some subclasses of Writer class are as follows :

Classes	Description
BufferedWriter	BufferedWriter class provides the facility to write texts to a character-output stream using buffer.
CharArrayWriter	CharArrayWriter implements the character buffer to write character stream.
FilterWriter	This class is used for writing the filtered character streams.
OutputStreamWriter	This class acts as a bridge from character streams to byte streams.
PipedWriter	Piped character output stream
PrintWriter	This class is used to write the formatted representation of objects to a text output stream.
StringWriter	This class writes a constructed string. String is constructed after collecting the output of a character stream into a buffer.

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