public class BufferedReader
extends java.io.Reader
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.
InputStreamReader
Constructor and Description |
---|
BufferedReader(java.io.Reader in)
Creates a buffering character-input stream that uses a default-sized input buffer.
|
BufferedReader(java.io.Reader in,
int sz)
Creates a buffering character-input stream that uses an input buffer of the specified size.
|
Modifier and Type | Method and Description |
---|---|
void |
close() |
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.
|
java.lang.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.
|
public BufferedReader(java.io.Reader in, int sz)
in
- A Readersz
- Input-buffer sizejava.lang.IllegalArgumentException
- If sz <= 0
public BufferedReader(java.io.Reader in)
in
- A Readerpublic int read() throws java.io.IOException
read
in class java.io.Reader
IOException
- If an I/O error occurspublic int read(char[] cbuf, int off, int len) throws java.io.IOException
This method implements the general contract of the corresponding
method of the read
class. As an
additional convenience, it attempts to read as many characters as possible by repeatedly invoking the
Reader
read
method of the underlying stream. This iterated read
continues until one of the
following conditions becomes true:
read
method of the underlying stream returns -1
, indicating end-of-file, or
ready
method of the underlying stream returns false
, 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.
read
in class java.io.Reader
cbuf
- Destination bufferoff
- Offset at which to start storing characterslen
- Maximum number of characters to readIOException
- If an I/O error occurspublic java.lang.String readLine() throws java.io.IOException
IOException
- If an I/O error occurspublic long skip(long n) throws java.io.IOException
skip
in class java.io.Reader
n
- The number of characters to skipjava.lang.IllegalArgumentException
- If n
is negative.IOException
- If an I/O error occurspublic boolean ready() throws java.io.IOException
ready
in class java.io.Reader
IOException
- If an I/O error occurspublic boolean markSupported()
markSupported
in class java.io.Reader
public void mark(int readAheadLimit) throws java.io.IOException
mark
in class java.io.Reader
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.java.lang.IllegalArgumentException
- If readAheadLimit < 0
IOException
- If an I/O error occurspublic void reset() throws java.io.IOException
reset
in class java.io.Reader
IOException
- If the stream has never been marked, or if the mark has been invalidatedpublic void close() throws java.io.IOException
close
in interface java.io.Closeable
close
in interface java.lang.AutoCloseable
close
in class java.io.Reader
java.io.IOException