Class PushbackReader
- java.lang.Object
-
- java.io.Reader
-
- java.io.FilterReader
-
- java.io.PushbackReader
- All Implemented Interfaces:
-
Closeable
,AutoCloseable
,Readable
public class PushbackReader extends FilterReader
A character-stream reader that allows characters to be pushed back into the stream.
- Since:
- 1.1
Field Summary
Fields declared in class java.io.FilterReader
in
Fields declared in class java.io.Reader
lock
Constructor Summary
Constructor | Description |
---|---|
PushbackReader(Reader in) | Creates a new pushback reader with a one-character pushback buffer. |
PushbackReader(Reader in,
int size) | Creates a new pushback reader with a pushback buffer of the given size. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
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 not. |
int | read() | Reads a single character. |
int | read(char[] cbuf,
int off,
int len) | Reads characters into a portion of an array. |
boolean | ready() | Tells whether this stream is ready to be read. |
void | reset() | Resets the stream. |
long | skip(long n) | Skips characters. |
void | unread(char[] cbuf) | Pushes back an array of characters by copying it to the front of the pushback buffer. |
void | unread(char[] cbuf,
int off,
int len) | Pushes back a portion of an array of characters by copying it to the front of the pushback buffer. |
void | unread(int c) | Pushes back a single character by copying it to the front of the pushback buffer. |
Methods declared in class java.io.Reader
nullReader, read, read, transferTo
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Constructor Detail
PushbackReader
public PushbackReader(Reader in, int size)
Creates a new pushback reader with a pushback buffer of the given size.
- Parameters:
-
in
- The reader from which characters will be read -
size
- The size of the pushback buffer - Throws:
-
IllegalArgumentException
- ifsize <= 0
PushbackReader
public PushbackReader(Reader in)
Creates a new pushback reader with a one-character pushback buffer.
- Parameters:
-
in
- The reader from which characters will be read
Method Detail
read
public int read() throws IOException
Reads a single character.
- Overrides:
-
read
in classFilterReader
- Returns:
- The character read, 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.
- Overrides:
-
read
in classFilterReader
- Parameters:
-
cbuf
- Destination buffer -
off
- Offset at which to start writing 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 -
IndexOutOfBoundsException
- If an I/O error occurs
unread
public void unread(int c) throws IOException
Pushes back a single character by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value (char)c
.
- Parameters:
-
c
- The int value representing a character to be pushed back - Throws:
-
IOException
- If the pushback buffer is full, or if some other I/O error occurs
unread
public void unread(char[] cbuf, int off, int len) throws IOException
Pushes back a portion of an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[off]
, the character after that will have the value cbuf[off+1]
, and so forth.
- Parameters:
-
cbuf
- Character array -
off
- Offset of first character to push back -
len
- Number of characters to push back - Throws:
-
IOException
- If there is insufficient room in the pushback buffer, or if some other I/O error occurs
unread
public void unread(char[] cbuf) throws IOException
Pushes back an array of characters by copying it to the front of the pushback buffer. After this method returns, the next character to be read will have the value cbuf[0]
, the character after that will have the value cbuf[1]
, and so forth.
- Parameters:
-
cbuf
- Character array to push back - Throws:
-
IOException
- If there is insufficient room in the pushback buffer, or if some other I/O error occurs
ready
public boolean ready() throws IOException
Tells whether this stream is ready to be read.
- Overrides:
-
ready
in classFilterReader
- 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
mark
public void mark(int readAheadLimit) throws IOException
Marks the present position in the stream. The mark
for class PushbackReader
always throws an exception.
- Overrides:
-
mark
in classFilterReader
- Parameters:
-
readAheadLimit
- Limit on the number of characters that may be read while still preserving the mark. After reading this many characters, attempting to reset the stream may fail. - Throws:
-
IOException
- Always, since mark is not supported
reset
public void reset() throws IOException
Resets the stream. The reset
method of PushbackReader
always throws an exception.
- Overrides:
-
reset
in classFilterReader
- Throws:
-
IOException
- Always, since reset is not supported
markSupported
public boolean markSupported()
Tells whether this stream supports the mark() operation, which it does not.
- Overrides:
-
markSupported
in classFilterReader
- Returns:
- true if and only if this stream supports the mark operation.
close
public void close() throws IOException
Closes the stream and releases any system resources associated with it. Once the stream has been closed, further read(), unread(), ready(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect. This method will block while there is another thread blocking on the reader.
- Specified by:
-
close
in interfaceAutoCloseable
- Specified by:
-
close
in interfaceCloseable
- Specified by:
-
close
in classReader
- Throws:
-
IOException
- If an I/O error occurs
skip
public long skip(long n) throws IOException
Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached.
- Overrides:
-
skip
in classFilterReader
- Parameters:
-
n
- The number of characters to skip - Returns:
- The number of characters actually skipped
- Throws:
-
IllegalArgumentException
- Ifn
is negative. -
IOException
- If an I/O error occurs