Skip to content

Most visited

Recently visited

navigation
Added in API level 1

BufferedReader

public class BufferedReader
extends Reader

java.lang.Object
   ↳ java.io.Reader
     ↳ java.io.BufferedReader
Known Direct Subclasses


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.

See also:

Summary

Inherited fields

From class java.io.Reader

Public constructors

BufferedReader(Reader in, int sz)

Creates a buffering character-input stream that uses an input buffer of the specified size.

BufferedReader(Reader in)

Creates a buffering character-input stream that uses a default-sized input buffer.

Public methods

void close()

Closes the stream and releases any system resources associated with it.

Stream<String> lines()

Returns a Stream, the elements of which are lines read from this BufferedReader.

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.

Inherited methods

From class java.io.Reader
From class java.lang.Object
From interface java.lang.Readable
From interface java.io.Closeable
From interface java.lang.AutoCloseable

Public constructors

BufferedReader

Added in API level 1
BufferedReader (Reader in, 
                int sz)

Creates a buffering character-input stream that uses an input buffer of the specified size.

Parameters
in Reader: A Reader
sz int: Input-buffer size
Throws
IllegalArgumentException If sz is <= 0

BufferedReader

Added in API level 1
BufferedReader (Reader in)

Creates a buffering character-input stream that uses a default-sized input buffer.

Parameters
in Reader: A Reader

Public methods

close

Added in API level 1
void close ()

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.

Throws
IOException

lines

Added in API level 24
Stream<String> lines ()

Returns a Stream, the elements of which are lines read from this BufferedReader. The Stream 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 underlying BufferedReader, it is wrapped in an UncheckedIOException which will be thrown from the Stream 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
Stream<String> a Stream<String> providing the lines of text described by this BufferedReader

mark

Added in API level 1
void mark (int readAheadLimit)

Marks the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point.

Parameters
readAheadLimit int: 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 If readAheadLimit is < 0
IOException If an I/O error occurs

markSupported

Added in API level 1
boolean markSupported ()

Tells whether this stream supports the mark() operation, which it does.

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

read

Added in API level 1
int read ()

Reads a single character.

Returns
int 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

Added in API level 1
int read (char[] cbuf, 
                int off, 
                int len)

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.

Parameters
cbuf char: Destination buffer
off int: Offset at which to start storing characters
len int: Maximum number of characters to read
Returns
int 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

Added in API level 1
String 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'), or a carriage return followed immediately by a linefeed.

Returns
String 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

See also:

ready

Added in API level 1
boolean 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.

Returns
boolean 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

reset

Added in API level 1
void reset ()

Resets the stream to the most recent mark.

Throws
IOException If the stream has never been marked, or if the mark has been invalidated

skip

Added in API level 1
long skip (long n)

Skips characters.

Parameters
n long: The number of characters to skip
Returns
long The number of characters actually skipped
Throws
IllegalArgumentException If n is negative.
IOException If an I/O error occurs
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.