Java IO.pdf - Nguyen Dang Binh

Java I/O
BufferedReader is notable for its readLine() method that allows you to read text a line at a
time. This replaces the common but deprecated readLine() method in DataInputStream.
Each time you read from an unbuffered reader, there's a matching read from the underlying
input stream. Therefore, it's a good idea to wrap a BufferedReader around each reader whose
read() operations are expensive, such as a FileReader. For example:
BufferedReader br = new BufferedReader(new FileReader("37.html"));
There are two constructors. One has a default buffer size (8192 characters); the other requires
the programmer to specify the buffer size:
public BufferedReader(Reader in, int buffer_size)
public BufferedReader(Reader in)
BufferedReader overrides most of its superclass's methods, including:
public int read() throws IOException
public int read(char[] text, int offset, int length) throws IOException
public long skip(long n) throws IOException
public boolean ready() throws IOException
In Java 2 and later, the two multicharacter read() methods try to completely fill the specified
array or subarray of text by reading repeatedly from the underlying reader. They return only
when the requested number of characters have been read, the end of the data is reached, or the
underlying reader would block. This is not the case for most readers (including buffered
readers in Java 1.1.x), which only attempt one read from the underlying data source before
returning.
BufferedReader does support marking and resetting, at least up to the length of the buffer:
public boolean markSupported()
public void mark(int readAheadLimit) throws IOException
public void reset() throws IOException
The one new method in this class is readLine():
public String readLine() throws IOException
This method returns a string that contains a line of text from a text file. \r, \n, and \r\n are
assumed to be line breaks and are not included in the returned string. This method is often
used when reading user input from System.in, since most platforms only send the user's
input to the running program after the user has typed a full line (that is, hit the Return key).
readLine() has the same problem with line ends that DataInputStream's readLine()
method has; that is, the potential to hang on a lone carriage return that ends the stream. This
problem is especially acute on networked connections, where readLine() should never be
used.
Example 15.5 uses a BufferedReader and readLine() to read all files named on the
command line, line by line, and copy them to System.out. In essence it implements the Unix
cat or the DOS type utility.
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