Reader (Java Platform SE 7 ) (original) (raw)
- java.io.Reader
All Implemented Interfaces:
Closeable, AutoCloseable, Readable
Direct Known Subclasses:
BufferedReader, CharArrayReader, FilterReader, InputStreamReader, PipedReader, StringReader
public abstract class Reader
extends Object
implements Readable, Closeable
Abstract class for reading character streams. The only methods that a subclass must implement are read(char[], int, int) and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both.
Since:
JDK1.1
See Also:
BufferedReader, LineNumberReader, CharArrayReader, InputStreamReader, FileReader, FilterReader, PushbackReader, PipedReader, StringReader, Writer
Field Summary
Fields
Modifier and Type Field and Description protected Object lock The object used to synchronize operations on this stream. Constructor Summary
Constructors
Modifier Constructor and Description protected Reader() Creates a new character-stream reader whose critical sections will synchronize on the reader itself. protected Reader(Object lock) Creates a new character-stream reader whose critical sections will synchronize on the given object. Method Summary
Methods
Modifier and Type Method and Description abstract 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. int read() Reads a single character. int read(char[] cbuf) Reads characters into an array. abstract int read(char[] cbuf, int off, int len) Reads characters into a portion of an array. int read(CharBuffer target) Attempts to read characters into the specified character buffer. boolean ready() Tells whether this stream is ready to be read. void reset() Resets the stream. long skip(long n) Skips characters. * ### Methods inherited from class java.lang.[Object](../../java/lang/Object.html "class in java.lang") `[clone](../../java/lang/Object.html#clone%28%29), [equals](../../java/lang/Object.html#equals%28java.lang.Object%29), [finalize](../../java/lang/Object.html#finalize%28%29), [getClass](../../java/lang/Object.html#getClass%28%29), [hashCode](../../java/lang/Object.html#hashCode%28%29), [notify](../../java/lang/Object.html#notify%28%29), [notifyAll](../../java/lang/Object.html#notifyAll%28%29), [toString](../../java/lang/Object.html#toString%28%29), [wait](../../java/lang/Object.html#wait%28%29), [wait](../../java/lang/Object.html#wait%28long%29), [wait](../../java/lang/Object.html#wait%28long,%20int%29)`Field Detail
* #### lock protected [Object](../../java/lang/Object.html "class in java.lang") lock The object used to synchronize operations on this stream. For efficiency, a character-stream object may use an object other than itself to protect critical sections. A subclass should therefore use the object in this field rather than this or a synchronized method.Constructor Detail
* #### Reader protected Reader() Creates a new character-stream reader whose critical sections will synchronize on the reader itself. * #### Reader protected Reader([Object](../../java/lang/Object.html "class in java.lang") lock) Creates a new character-stream reader whose critical sections will synchronize on the given object. Parameters: `lock` \- The Object to synchronize on.Method Detail
* #### read public int read([CharBuffer](../../java/nio/CharBuffer.html "class in java.nio") target) throws [IOException](../../java/io/IOException.html "class in java.io") Attempts to read characters into the specified character buffer. The buffer is used as a repository of characters as-is: the only changes made are the results of a put operation. No flipping or rewinding of the buffer is performed. **Specified by:** `[read](../../java/lang/Readable.html#read%28java.nio.CharBuffer%29)` in interface `[Readable](../../java/lang/Readable.html "interface in java.lang")` Parameters: `target` \- the buffer to read characters into Returns: The number of characters added to the buffer, or -1 if this source of characters is at its end Throws: `[IOException](../../java/io/IOException.html "class in java.io")` \- if an I/O error occurs `[NullPointerException](../../java/lang/NullPointerException.html "class in java.lang")` \- if target is null `ReadOnlyBufferException` \- if target is a read only buffer Since: 1.5 * #### read public int read() throws [IOException](../../java/io/IOException.html "class in java.io") Reads a single character. This method will block until a character is available, an I/O error occurs, or the end of the stream is reached. Subclasses that intend to support efficient single-character input should override this method. 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](../../java/io/IOException.html "class in java.io")` \- If an I/O error occurs * #### read public int read(char[] cbuf) throws [IOException](../../java/io/IOException.html "class in java.io") Reads characters into an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached. Parameters: `cbuf` \- Destination buffer Returns: The number of characters read, or -1 if the end of the stream has been reached Throws: `[IOException](../../java/io/IOException.html "class in java.io")` \- If an I/O error occurs * #### read public abstract int read(char[] cbuf, int off, int len) throws [IOException](../../java/io/IOException.html "class in java.io") Reads characters into a portion of an array. This method will block until some input is available, an I/O error occurs, or the end of the stream is reached. Parameters: `cbuf` \- Destination buffer `off` \- Offset at which to start storing 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](../../java/io/IOException.html "class in java.io")` \- If an I/O error occurs * #### skip public long skip(long n) throws [IOException](../../java/io/IOException.html "class in java.io") Skips characters. This method will block until some characters are available, an I/O error occurs, or the end of the stream is reached. Parameters: `n` \- The number of characters to skip Returns: The number of characters actually skipped Throws: `[IllegalArgumentException](../../java/lang/IllegalArgumentException.html "class in java.lang")` \- If `n` is negative. `[IOException](../../java/io/IOException.html "class in java.io")` \- If an I/O error occurs * #### ready public boolean ready() throws [IOException](../../java/io/IOException.html "class in java.io") Tells whether this stream is ready to be read. 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](../../java/io/IOException.html "class in java.io")` \- If an I/O error occurs * #### markSupported public boolean markSupported() Tells whether this stream supports the mark() operation. The default implementation always returns false. Subclasses should override this method. Returns: true if and only if this stream supports the mark operation. * #### mark public void mark(int readAheadLimit) throws [IOException](../../java/io/IOException.html "class in java.io") Marks the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point. Not all character-input streams support the mark() operation. 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](../../java/io/IOException.html "class in java.io")` \- If the stream does not support mark(), or if some other I/O error occurs * #### reset public void reset() throws [IOException](../../java/io/IOException.html "class in java.io") Resets the stream. If the stream has been marked, then attempt to reposition it at the mark. If the stream has not been marked, then attempt to reset it in some way appropriate to the particular stream, for example by repositioning it to its starting point. Not all character-input streams support the reset() operation, and some support reset() without supporting mark(). Throws: `[IOException](../../java/io/IOException.html "class in java.io")` \- If the stream has not been marked, or if the mark has been invalidated, or if the stream does not support reset(), or if some other I/O error occurs * #### close public abstract void close() throws [IOException](../../java/io/IOException.html "class in java.io") 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](../../java/io/Closeable.html#close%28%29)` in interface `[Closeable](../../java/io/Closeable.html "interface in java.io")` **Specified by:** `[close](../../java/lang/AutoCloseable.html#close%28%29)` in interface `[AutoCloseable](../../java/lang/AutoCloseable.html "interface in java.lang")` Throws: `[IOException](../../java/io/IOException.html "class in java.io")` \- If an I/O error occurs
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