Class BufferedReader
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Readable
- Direct Known Subclasses:
LineNumberReader
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
FileReader
s and InputStreamReader
s. For
example,
BufferedReader in = new BufferedReader(new FileReader("foo.in"));
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 DataInputStream
s for textual input can be
localized by replacing each DataInputStream
with an appropriate
BufferedReader
.
- API Note:
- Once wrapped in a
BufferedReader
, the underlyingReader
should not be used directly nor wrapped with another reader. - Since:
- 1.1
- See Also:
-
Field Summary
-
Constructor Summary
ConstructorDescriptionBufferedReader
(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
Modifier and TypeMethodDescriptionvoid
close()
Closes the stream and releases any system resources associated with it.lines()
Returns aStream
, the elements of which are lines read from thisBufferedReader
.void
mark
(int readAheadLimit) Marks the present position in the stream.boolean
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.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.Methods declared in class java.io.Reader
nullReader, read, read, skip, transferTo
-
Constructor Details
-
BufferedReader
Creates a buffering character-input stream that uses an input buffer of the specified size.- Parameters:
in
- A Readersz
- Input-buffer size- Throws:
IllegalArgumentException
- Ifsz <= 0
-
BufferedReader
Creates a buffering character-input stream that uses a default-sized input buffer.- Parameters:
in
- A Reader
-
-
Method Details
-
read
Reads a single character.- Overrides:
read
in classReader
- 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
Reads characters into a portion of an array.This method implements the general contract of the corresponding
read
method of theReader
class. As an additional convenience, it attempts to read as many characters as possible by repeatedly invoking theread
method of the underlying stream. This iteratedread
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 returnsfalse
, indicating that further input requests would block.
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
BufferedReader
s will not copy data unnecessarily.- Specified by:
read
in classReader
- Parameters:
cbuf
- Destination bufferoff
- Offset at which to start storing characterslen
- Maximum number of characters to read- Returns:
- The number of characters read, or -1 if the end of the stream has been reached
- Throws:
IndexOutOfBoundsException
- Ifoff
is negative, orlen
is negative, orlen
is greater thancbuf.length - off
IOException
- If an I/O error occurs
-
readLine
Reads a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), a carriage return followed immediately by a line feed, or by reaching the end-of-file (EOF).- 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 without reading any characters
- Throws:
IOException
- If an I/O error occurs- See Also:
-
ready
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 classReader
- 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 classReader
- Returns:
- true if and only if this stream supports the mark operation.
-
mark
Marks the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point.- Overrides:
mark
in classReader
- Parameters:
readAheadLimit
- Limit on the number of characters that may be read while still preserving the mark. An attempt 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
- IfreadAheadLimit < 0
IOException
- If an I/O error occurs
-
reset
Resets the stream to the most recent mark.- Overrides:
reset
in classReader
- Throws:
IOException
- If the stream has never been marked, or if the mark has been invalidated
-
close
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 interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in classReader
- Throws:
IOException
- If an I/O error occurs
-
lines
Returns aStream
, the elements of which are lines read from thisBufferedReader
. TheStream
is lazily populated, i.e., read only occurs during the terminal stream operation.The reader must not be operated on during the execution of the terminal stream operation. Otherwise, the result of the terminal stream operation is undefined.
After execution of the terminal stream operation there are no guarantees that the reader will be at a specific position from which to read the next character or line.
If an
IOException
is thrown when accessing the underlyingBufferedReader
, it is wrapped in anUncheckedIOException
which will be thrown from theStream
method that caused the read to take place. This method will return a Stream if invoked on a BufferedReader that is closed. Any operation on that stream that requires reading from the BufferedReader after it is closed, will cause an UncheckedIOException to be thrown.- Returns:
- a
Stream<String>
providing the lines of text described by thisBufferedReader
- Since:
- 1.8
-