Character streams with its types

Character Streams:

Byte streams are used to perform input and output of 8-bit bytes
Character streams are used to perform input and output for 16-bit Unicode.
All byte stream classes are descended from Reader and Writer.
Figure:

There are many Character stream classes.
When Not to Use Byte Streams?

When .txt contains character data, the best approach is to use character streams.
There are also streams for more complicated data types.
Byte streams should only be used for the most primitive I/O.

Why talk about byte streams?

Because all other stream types are built on byte streams.
Character streams are often "wrappers" for byte streams.
The character stream uses the byte stream to perform the physical I/O, while the character stream handles translation between characters and bytes.
For Example:

FileReader uses FileInputStream, while FileWriter uses FileOutputStream.
There are two general-purpose byte-to-character "bridge" streams: InputStreamReader and OutputStreamWriter.

Example: Classes of Reader and Writer stream:

Reader Class:

Syntax:
java.lang.Object
java.io.Reader
Abstract class for reading character streams.
The only methods that a subclass must implement are read(char[], int, int) and close().
It has one field, two constructors and seven methods.
Field:

protected Object lock

Constructor:

protected Reader()
protected Reader(Object lock)

Methods:

1. close
- Syntax: public abstract void close() throws IOException
- Use: Closes the stream and releases any system resources associated with it.
- Throws: IOException - If an I/O error occurs
2. mark

Syntax: public void mark(int readAheadLimit) throws IOException
Use: Marks the present position in the stream. Not all character-input streams support the mark() operation.
Parameters: readAheadLimit - Limit on the number of characters that may be read while still preserving the mark.
Throws: IOException - If the stream does not support mark(), or if some other I/O error occurs

3. markSupported
- Syntax: public boolean markSupported()

Use: Tells whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method.

Returns: true if and only if this stream supports the mark operation.

4. read
- Syntax:
- Use:
- Parameters:
- Returns:
- Throws:

NullPointerException - if target is null
ReadOnlyBufferException - if target is a read-only buffer

5. ready

Syntax: public boolean ready() throws IOException

Use: Tells whether this stream is ready to be read.

Returns: True if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.

Throws: IOException - If an I/O error occurs

6. reset

Syntax: public void reset() throws IOException
Use: Resets the stream. Not all character-input streams support the reset() operation, and some support reset() without supporting mark().
Throws: IOException - If the stream has not been marked, or if the mark has been invalidated, or if the stream does not support reset(), or if some other I/O error occurs

7. skip
- Syntax: public long skip(long n) throws IOException
- Use: Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached.
- Parameters: n - The number of characters to skip
- Returns: The number of characters actually skipped
- Throws:

Writer Class:

Syntax:
java.lang.Object
java.io.Writer
Abstract class for writing to character streams.
The only methods that a subclass must implement are write(char[], int, int), flush(), and close().
It has one field, two constructors and four methods.
Field:

protected Object lock

Constructor:

protected Writer()
protected Writer(Object lock)

Methods:

1. append

Syntax:

public Writer append(char c) throws IOException
public Writer append(CharSequence csq) throws IOException
public Writer append(CharSequence csq, int start, int end) throws IOException

Use:

Appends the specified character to this writer.
An invocation of this method of the form out.append(c) behaves in exactly the same way as the invocation: out.write(c)
Appends the specified character sequence to this writer.
An invocation of this method of the form out.append(csq) behaves in exactly the same way as the invocation: out.write(csq.toString())
Appends a subsequence of the specified character sequence to this writer.
An invocation of this method of the form out.append(csq, start, end) when csq is not null behaves in exactly the same way as the invocation: out.write(csq.subSequence(start, end).toString())

Parameters:

c - The 16-bit character to append
csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.
start - The index of the first character in the subsequence
end - The index of the character following the last character in the subsequence

Returns:

This writer

Throws:

IOException - If an I/O error occurs
IndexOutOfBoundsException - If start or end are negative, start is greater than end, or end is greater than csq.length()

2. close
- Syntax: public abstract void close() throws IOException

Use: Closes the stream, flushing it first.
Throws: IOException - If an I/O error occurs

3. flush
- Syntax: public abstract void flush() throws IOException
- Use: Flushes the stream.
- Throws: IOException - If an I/O error occurs
4. write

Syntax:

public void write(char[] cbuf) throws IOException
public abstract void write(char[] cbuf, int off, int len) throws IOException
public void write(int c) throws IOException
public void write(String str) throws IOException
public void write(String str, int off, int len) throws IOException

Use:

Writes an array of characters.
Writes a portion of an array of characters.
Writes a single character. The character to be written is contained in the 16 low-order bits of the given integer value; the 16 high-order bits are ignored.
Writes a string.
Writes a portion of a string.

Parameters:

cbuf - Array of characters to be written
off - Offset from which to start writing characters
len - Number of characters to write
c - int specifying a character to be written
str - String to be written

Throws:

IndexOutOfBoundsException - If off is negative, or len is negative, or off+len is negative or greater than the length of the given string
IOException - If an I/O error occurs.

Example (Read File):