public abstract class Reader extends Object implements Readable, Closeable
This abstract class does not provide a fully working implementation, so it
needs to be subclassed, and at least the read(char[], int, int)
and
close()
methods needs to be overridden. Overriding some of the
non-abstract methods is also often advised, since it might result in higher
efficiency.
Many specialized readers for purposes like reading from a file already exist in this package.
Writer
Modifier and Type | Field and Description |
---|---|
protected Object |
lock
The object used to synchronize access to the reader.
|
Modifier | Constructor and Description |
---|---|
protected |
Reader()
Constructs a new
Reader with this as the object used to
synchronize critical sections. |
protected |
Reader(Object lock)
Constructs a new
Reader with lock used to synchronize
critical sections. |
Modifier and Type | Method and Description |
---|---|
abstract void |
close()
Closes this reader.
|
void |
mark(int readLimit)
Sets a mark position in this reader.
|
boolean |
markSupported()
Indicates whether this reader supports the
mark() and
reset() methods. |
int |
read()
Reads a single character from this reader and returns it as an integer
with the two higher-order bytes set to 0.
|
int |
read(char[] buf)
Reads characters from this reader and stores them in the character array
buf starting at offset 0. |
abstract int |
read(char[] buf,
int offset,
int count)
Reads at most
count characters from this reader and stores them
at offset in the character array buf . |
int |
read(CharBuffer target)
Reads characters and puts them into the
target character buffer. |
boolean |
ready()
Indicates whether this reader is ready to be read without blocking.
|
void |
reset()
Resets this reader's position to the last
mark() location. |
long |
skip(long charCount)
Skips
charCount characters in this reader. |
protected Object lock
protected Reader()
Reader
with this
as the object used to
synchronize critical sections.protected Reader(Object lock)
Reader
with lock
used to synchronize
critical sections.lock
- the Object
used to synchronize critical sections.NullPointerException
- if lock
is null
.public abstract void close() throws IOException
close
in interface Closeable
close
in interface AutoCloseable
IOException
- if an error occurs while closing this reader.public void mark(int readLimit) throws IOException
readLimit
indicates how many characters can be read before the mark is invalidated.
Calling reset()
will reposition the reader back to the marked
position if readLimit
has not been surpassed.
This default implementation simply throws an IOException
;
subclasses must provide their own implementation.
readLimit
- the number of characters that can be read before the mark is
invalidated.IllegalArgumentException
- if readLimit < 0
.IOException
- if an error occurs while setting a mark in this reader.markSupported()
,
reset()
public boolean markSupported()
mark()
and
reset()
methods. This default implementation returns
false
.false
.public int read() throws IOException
IOException
- if this reader is closed or some other I/O error occurs.public int read(char[] buf) throws IOException
buf
starting at offset 0. Returns the number of characters
actually read or -1 if the end of the reader has been reached.buf
- character array to store the characters read.IOException
- if this reader is closed or some other I/O error occurs.public abstract int read(char[] buf, int offset, int count) throws IOException
count
characters from this reader and stores them
at offset
in the character array buf
. Returns the number
of characters actually read or -1 if the end of the reader has been
reached.buf
- the character array to store the characters read.offset
- the initial position in buffer
to store the characters
read from this reader.count
- the maximum number of characters to read.IOException
- if this reader is closed or some other I/O error occurs.public boolean ready() throws IOException
true
if this reader will not block when read
is
called, false
if unknown or blocking will occur. This default
implementation always returns false
.false
.IOException
- if this reader is closed or some other I/O error occurs.read()
,
read(char[])
,
read(char[], int, int)
public void reset() throws IOException
mark()
location.
Invocations of read()
and skip()
will occur from this new
location. If this reader has not been marked, the behavior of
reset()
is implementation specific. This default
implementation throws an IOException
.IOException
- always thrown in this default implementation.mark(int)
,
markSupported()
public long skip(long charCount) throws IOException
charCount
characters in this reader. Subsequent calls of
read
methods will not return these characters unless reset
is used. This method may perform multiple reads to read charCount
characters.IllegalArgumentException
- if charCount < 0
.IOException
- if this reader is closed or some other I/O error occurs.mark(int)
,
markSupported()
,
reset()
public int read(CharBuffer target) throws IOException
target
character buffer.read
in interface Readable
target
- the destination character buffer.target
or -1 if the end
of this reader has been reached before a character has been read.IOException
- if any I/O error occurs while reading from this reader.NullPointerException
- if target
is null
.ReadOnlyBufferException
- if target
is read-only.