Android
java.io
public abstract class

java.io.Reader

java.lang.Object
java.io.Reader Closeable Readable

Reader is an Abstract class for reading Character Streams. Subclasses of Reader must implement the methods read(char[], int, int) and close().

Known Direct Subclasses
Known Indirect Subclasses

See Also

Summary

Fields

protected      Object  lock  The object used to synchronize access to the reader. 

Protected Constructors

            Reader()
Constructs a new character stream Reader using this as the Object to synchronize critical regions around.
            Reader(Object lock)
Constructs a new character stream Reader using lock as the Object to synchronize critical regions around.

Public Methods

abstract          void  close()
Close this Reader.
          void  mark(int readLimit)
Set a Mark position in this Reader.
          boolean  markSupported()
Returns a boolean indicating whether or not this Reader supports mark() and reset().
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)
Read chars from the Reader and then put them to the target CharBuffer.
          int  read(char[] buf)
Reads characters from this Reader and stores them in the character array buf starting at offset 0.
          int  read()
Reads a single character from this reader and returns the result as an int.
          boolean  ready()
Returns a boolean indicating whether or not this Reader is ready to be read without blocking.
          void  reset()
Reset this Readers position to the last mark() location.
          long  skip(long count)
Skips count number of characters in this Reader.
Methods inherited from class java.lang.Object
Methods inherited from interface java.io.Closeable
Methods inherited from interface java.lang.Readable

Details

Fields

protected Object lock

The object used to synchronize access to the reader.

Protected Constructors

protected Reader()

Constructs a new character stream Reader using this as the Object to synchronize critical regions around.

protected Reader(Object lock)

Constructs a new character stream Reader using lock as the Object to synchronize critical regions around.

Parameters

lock the Object to synchronize critical regions around.

Public Methods

public abstract void close()

Close this Reader. This must be implemented by any concrete subclasses. The implementation should free any resources associated with the Reader.

Throws

IOException If an error occurs attempting to close this Reader.

public void mark(int readLimit)

Set a Mark position in this Reader. The parameter readLimit indicates how many characters can be read before a mark is invalidated. Sending reset() will reposition the reader back to the marked position provided readLimit has not been surpassed.

This default implementation simply throws IOException and concrete subclasses must provide their own implementations.

Parameters

readLimit an int representing how many characters must be read before invalidating the mark.

Throws

IOException If an error occurs attempting mark this Reader.

public boolean markSupported()

Returns a boolean indicating whether or not this Reader supports mark() and reset(). This class a default implementation which returns false.

Returns

  • true if mark() and reset() are supported, false otherwise. This implementation returns false.

public 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. Returns the number of characters actually read or -1 if the end of reader was encountered.

Parameters

buf character array to store the read characters
offset offset in buf to store the read characters
count how many characters should be read in

Returns

  • how many characters were successfully read in or else -1 if the end of the reader was detected.

Throws

IOException If the Reader is already closed or some other IO error occurs.

public int read(CharBuffer target)

Read chars from the Reader and then put them to the target CharBuffer. Only put method is called on the target.

Parameters

target the destination CharBuffer

Returns

  • the actual number of chars put to the target. -1 when the Reader has reached the end before the method is called.

Throws

IOException if any I/O error raises in the procedure
NullPointerException if the target CharBuffer is null
ReadOnlyBufferException if the target CharBuffer is readonly

public int read(char[] buf)

Reads characters from this Reader and stores them in the character array buf starting at offset 0. Returns the number of characters actually read or -1 if the end of reader was encountered.

Parameters

buf character array to store the read characters

Returns

  • how many characters were successfully read in or else -1 if the end of the reader was detected.

Throws

IOException If the Reader is already closed or some other IO error occurs.

public int read()

Reads a single character from this reader and returns the result as an int. The 2 higher-order characters are set to 0. If the end of reader was encountered then return -1.

Returns

  • the character read or -1 if end of reader.

Throws

IOException If the Reader is already closed or some other IO error occurs.

public boolean ready()

Returns a boolean indicating whether or not this Reader is ready to be read without blocking. If the result is true, the next read() will not block. If the result is false this Reader may or may not block when read() is sent.

Returns

  • true if the receiver will not block when read() is called, false if unknown or blocking will occur.

Throws

IOException If the Reader is already closed or some other IO error occurs.

public void reset()

Reset this Readers position to the last mark() location. Invocations of read()/skip() will occur from this new location. If this Reader was not marked, the implementation of reset() is implementation specific. See the comment for the specific Reader subclass for implementation details. The default action is to throw IOException.

Throws

IOException If a problem occured or the receiver does not support mark()/reset().

public long skip(long count)

Skips count number of characters in this Reader. Subsequent read()'s will not return these characters unless reset() is used. This method may perform multiple reads to read count characters.

Parameters

count how many characters should be passed over

Returns

  • how many characters were successfully passed over

Throws

IOException If the Reader is closed when the call is made or if an IO error occurs during the operation.
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