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| Chapter 11 The java.io Package |

# StringReader

## Name

StringReader

## Synopsis

Class Name:

  `java.io.StringReader`

Superclass:

  `java.io.Reader`

Immediate Subclasses:

  None

Interfaces Implemented:

  None

Availability:

  New as of JDK 1.1

## Description

The `StringReader` class represents a character stream whose data source is a`String`. This class is similar to the `CharArrayReader` class, which uses a `char` array as its data source.

`StringReader` is meant to replace the `StringBufferInputStream` class as of JDK 1.1. Unlike `StringBufferInputStream`, `StringReader` handles Unicode characters and supports `mark()` and `reset()`.

## Class Summary

    public class java.io.StringReader extends java.io.Reader {
      // Constructors
      public StringReader(String s);
      // Instance Methods
      public void close();
      public void mark(int readAheadLimit);
      public boolean markSupported();
      public int read();
      public int read(char[] cbuf, int off, int len);
      public boolean ready();
      public void reset();
      public long skip(long ns);
    }

## Constructors

### StringReader

#### public StringReader(String s)

Parameters

  `s`

    The `String` to use.

Description

  This constructor creates a `StringReader` that uses the given `String` as its data source. The data is not copied, so changes made to the `String` affect the data that the `StringReader` returns.

## Instance Methods

### close

#### public void close()

Overrides

  `Reader.close()`

Description

  This method closes the reader by removing the link between this `StringReader` and the `String` it was created with.

### mark

#### public void mark(int readAheadLimit) throws IOException

Parameters

  `readAheadLimit`

    The maximum number of characters that can be read before the saved position becomes invalid.

Throws

  `IOException`

    If the stream is closed or any other kind of I/O error occurs.

Overrides

  `Reader.mark()`

Description

  This method causes the `StringReader` to remember its current position. A subsequent call to `reset()` causes the object to return to that saved position, and thus re-read a portion of the string. Because the data for this stream comes from a `String`, there is no limit on reading ahead, so `readAheadLimit` is ignored.

### markSupported

#### public boolean markSupported()

Returns

  The `boolean` value `true`.

Overrides

  `Reader.markSupported()`

Description

  This method returns `true` to indicate that this class supports `mark()` and `reset()`.

### read

#### public int read() throws IOException

Returns

  The next character or `-1` if the end of the string is encountered.

Throws

  `IOException`

    If the stream is closed or any other kind of I/O error occurs.

Overrides

  `Reader.read()`

Description

  This method returns the next character from the string. The method cannot block.

#### public int read(char[] cbuf, int off, int len) throws IOException

Parameters

  `cbuf`

    An array of characters to be filled from the stream.

  `off`

    An offset into the character array.

  `len`

    The number of characters to read.

Returns

  The actual number of characters read or `-1` if the end of the string is encountered immediately.

Throws

  `IOException`

    If the stream is closed or any other kind of I/O error occurs.

Overrides

  `Reader.read(char[], int, int)`

Description

  This method copies up to `len` characters from the internal buffer into the given array `cbuf`, starting at index `off`.

### ready

#### public boolean ready() throws IOException

Returns

  A `boolean` value that indicates whether the stream is ready to be read.

Throws

  `IOException`

    If the stream is closed or any other kind of I/O error occurs.

Overrides

  `Reader.ready()`

Description

  If there is any data left to be read from the string, this method returns `true`.

### reset

#### public void reset() throws IOException

Throws

  `IOException`

    If the stream is closed or any other kind of I/O error occurs.

Overrides

  `Reader.reset()`

Description

  This method resets the position of the `StringReader` to the position that was saved by calling the `mark()` method. If `mark()` has not been called, the `StringReader` is reset to read from the beginning of the string.

### skip

#### public long skip(long ns) throws IOException

Parameters

  `ns`

    The number of bytes to skip.

Returns

  The actual number of bytes skipped.

Throws

  `IOException`

    If the stream is closed or any other kind of I/O error occurs.

Overrides

  `Reader.skip()`

Description

  This method skips `ns` characters of input. If you try to skip past the end of the string, the stream is positioned at the end of the string.

## Inherited Methods

Method | Inherited From | Method | Inherited From
--- | --- | --- | ---
`clone()` | `Object` | `equals (Object)` | `Object`
`finalize()` | `Object` | `getClass()` | `Object`
`hashCode()` | `Object` | `notify()` | `Object`
`notifyAll()` | `Object` | `read(char[])` | `Reader`
`toString()` | `Object` | `wait()` | `Object`
`wait(long)` | `Object` | `wait(long, int)` | `Object`

## See Also

`CharArrayReader`, `IOException`, `Reader`, `String`, `StringBufferInputStream`

StringBufferInputStream |  | StringWriter