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java.io
Class BufferedReader
java.lang.Object
java.io.Reader
java.io.BufferedReader
-
All Implemented Interfaces:
-
Closeable
,
Readable
-
Direct Known Subclasses:
-
LineNumberReader
-
public class BufferedReader
- extends Reader
Reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.
The buffer size may be specified, or the default size may be used. The default is large enough for most purposes.
In general, each read request made of a Reader causes a corresponding read request to be made of the underlying character or byte stream. It is therefore advisable to wrap a BufferedReader around any Reader whose read() operations may be costly, such as FileReaders and InputStreamReaders. For example,
BufferedReader in
= new BufferedReader(new FileReader("foo.in"));
will buffer the input from the specified file. Without buffering, each invocation of read() or readLine() could cause bytes to be read from the file, converted into characters, and then returned, which can be very inefficient.
Programs that use DataInputStreams for textual input can be localized by replacing each DataInputStream with an appropriate BufferedReader.
-
Since:
-
JDK1.1
-
See Also:
-
FileReader
,
InputStreamReader
Constructor Summary
|
BufferedReader
(
Reader
in)
Creates a buffering character-input stream that uses a default-sized input buffer. |
BufferedReader
(
Reader
in, int sz)
Creates a buffering character-input stream that uses an input buffer of the specified size. |
Method Summary
|
void |
close
()
Closes the stream and releases any system resources associated with it. |
void |
mark
(int readAheadLimit)
Marks the present position in the stream. |
boolean |
markSupported
()
Tells whether this stream supports the mark() operation, which it does. |
int |
read
()
Reads a single character. |
int |
read
(char[] cbuf, int off, int len)
Reads characters into a portion of an array. |
String
|
readLine
()
Reads a line of text. |
boolean |
ready
()
Tells whether this stream is ready to be read. |
void |
reset
()
Resets the stream to the most recent mark. |
long |
skip
(long n)
Skips characters. |
Methods inherited from class java.lang.
Object
|
clone
,
equals
,
finalize
,
getClass
,
hashCode
,
notify
,
notifyAll
,
toString
,
wait
,
wait
,
wait
|
BufferedReader
public BufferedReader(Reader in,
int sz)
-
Creates a buffering character-input stream that uses an input buffer of the specified size.
-
Parameters:
-
in - A Reader
-
sz - Input-buffer size
-
Throws:
-
IllegalArgumentException
- If sz is <= 0
BufferedReader
public BufferedReader(Reader in)
-
Creates a buffering character-input stream that uses a default-sized input buffer.
-
Parameters:
-
in - A Reader
read
public int read()
throws IOException
-
Reads a single character.
-
-
Overrides:
-
read
in class
Reader
-
-
Returns:
-
The character read, as an integer in the range 0 to 65535 (
0x00-0xffff
), or -1 if the end of the stream has been reached
-
Throws:
-
IOException
- If an I/O error occurs
read
public int read(char[] cbuf,
int off,
int len)
throws IOException
-
Reads characters into a portion of an array.
This method implements the general contract of the corresponding
read
method of the
Reader
class. As an additional convenience, it attempts to read as many characters as possible by repeatedly invoking the read method of the underlying stream. This iterated read continues until one of the following conditions becomes true:
-
The specified number of characters have been read,
-
The read method of the underlying stream returns -1, indicating end-of-file, or
-
The ready method of the underlying stream returns false, indicating that further input requests would block.
If the first read on the underlying stream returns -1 to indicate end-of-file then this method returns -1. Otherwise this method returns the number of characters actually read.
Subclasses of this class are encouraged, but not required, to attempt to read as many characters as possible in the same fashion.
Ordinarily this method takes characters from this stream's character buffer, filling it from the underlying stream as necessary. If, however, the buffer is empty, the mark is not valid, and the requested length is at least as large as the buffer, then this method will read characters directly from the underlying stream into the given array. Thus redundant BufferedReaders will not copy data unnecessarily.
-
-
Specified by:
-
read
in class
Reader
-
-
Parameters:
-
cbuf - Destination buffer
-
off - Offset at which to start storing characters
-
len - Maximum number of characters to read
-
Returns:
-
The number of characters read, or -1 if the end of the stream has been reached
-
Throws:
-
IOException
- If an I/O error occurs
readLine
public String readLine()
throws IOException
-
Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.
-
-
Returns:
-
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached
-
Throws:
-
IOException
- If an I/O error occurs
skip
public long skip(long n)
throws IOException
-
Skips characters.
-
-
Overrides:
-
skip
in class
Reader
-
-
Parameters:
-
n - The number of characters to skip
-
Returns:
-
The number of characters actually skipped
-
Throws:
-
IllegalArgumentException
- If n is negative.
-
IOException
- If an I/O error occurs
ready
public boolean ready()
throws IOException
-
Tells whether this stream is ready to be read. A buffered character stream is ready if the buffer is not empty, or if the underlying character stream is ready.
-
-
Overrides:
-
ready
in class
Reader
-
-
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
markSupported
public boolean markSupported()
-
Tells whether this stream supports the mark() operation, which it does.
-
-
Overrides:
-
markSupported
in class
Reader
-
-
Returns:
-
true if and only if this stream supports the mark operation.
mark
public void mark(int readAheadLimit)
throws IOException
-
Marks the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point.
-
-
Overrides:
-
mark
in class
Reader
-
-
Parameters:
-
readAheadLimit - Limit on the number of characters that may be read while still preserving the mark.
An attempt
After reading this many characters, attempting
to reset the stream
after reading characters up to this limit or beyond
may fail. A limit value larger than the size of the input buffer will cause a new buffer to be allocated whose size is no smaller than limit. Therefore large values should be used with care. -
Throws:
-
IllegalArgumentException
- If readAheadLimit is < 0
-
IOException
- If an I/O error occurs
reset
public void reset()
throws IOException
-
Resets the stream to the most recent mark.
-
-
Overrides:
-
reset
in class
Reader
-
-
Throws:
-
IOException
- If the stream has never been marked, or if the mark has been invalidated
close
public void close()
throws IOException
-
Description copied from class:
Reader
-
Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.
-
-
Specified by:
-
close
in interface
Closeable
-
Specified by:
-
close
in class
Reader
-
-
Throws:
-
IOException
- If an I/O error occurs