NullReader (CommonsIO API)

java.lang.Object
- java.io.Reader
- - org.apache.commons.io.input.NullReader

所有已实现的接口:

Closeable, AutoCloseable, Readable
```
public class NullReader
extends Reader
```
A functional, light weight Reader that emulates a reader of a specified size.
This implementation provides a light weight object for testing with an Reader where the contents don't matter.
One use case would be for testing the handling of large Reader as it can emulate that scenario without the overhead of actually processing large numbers of characters - significantly speeding up test execution times.
This implementation returns a space from the method that reads a character and leaves the array unchanged in the read methods that are passed a character array. If alternative data is required the processChar() and processChars() methods can be implemented to generate data, for example:
```
  public class TestReader extends NullReader {
      public TestReader(int size) {
          super(size);
      }
      protected char processChar() {
          return ... // return required value here
      }
      protected void processChars(char[] chars, int offset, int length) {
          for (int i = offset; i < length; i++) {
              chars[i] = ... // set array value here
          }
      }
  }
 
```
从以下版本开始:

1.3

字段概要
- 从类继承的字段 java.io.Reader
  lock

构造器概要

构造器
构造器和说明
`NullReader(long size)` Create a `Reader` that emulates a specified size which supports marking and does not throw EOFException.
`NullReader(long size, boolean markSupported, boolean throwEofException)` Create a `Reader` that emulates a specified size with option settings.

方法概要

所有方法实例方法具体方法
限定符和类型	方法和说明
`void`	`close()` Close this Reader - resets the internal state to the initial values.
`long`	`getPosition()` Return the current position.
`long`	`getSize()` Return the size this `Reader` emulates.
`void`	`mark(int readlimit)` Mark the current position.
`boolean`	`markSupported()` Indicates whether mark is supported.
`protected int`	`processChar()` Return a character value for the `read()` method.
`protected void`	`processChars(char[] chars, int offset, int length)` Process the characters for the `read(char[], offset, length)` method.
`int`	`read()` Read a character.
`int`	`read(char[] chars)` Read some characters into the specified array.
`int`	`read(char[] chars, int offset, int length)` Read the specified number characters into an array.
`void`	`reset()` Reset the stream to the point when mark was last called.
`long`	`skip(long numberOfChars)` Skip a specified number of characters.

从类继承的方法 java.io.Reader
read, ready

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 构造器详细资料
  - NullReader
```
public NullReader(long size)
```
    Create a Reader that emulates a specified size which supports marking and does not throw EOFException.
    
    参数:
    
    size - The size of the reader to emulate.
  - NullReader
```
public NullReader(long size,
                  boolean markSupported,
                  boolean throwEofException)
```
    Create a Reader that emulates a specified size with option settings.
    
    参数:
    
    size - The size of the reader to emulate.
    
    markSupported - Whether this instance will support the mark() functionality.
    
    throwEofException - Whether this implementation will throw an EOFException or return -1 when the end of file is reached.
- 方法详细资料
  - getPosition
```
public long getPosition()
```
    Return the current position.
    
    返回:
    
    the current position.
  - getSize
```
public long getSize()
```
    Return the size this Reader emulates.
    
    返回:
    
    The size of the reader to emulate.
  - close
```
public void close()
           throws IOException
```
    Close this Reader - resets the internal state to the initial values.
    
    指定者:
    
    close 在接口中 Closeable
    
    指定者:
    
    close 在接口中 AutoCloseable
    
    指定者:
    
    close 在类中 Reader
    
    抛出:
    
    IOException - If an error occurs.
  - mark
```
public void mark(int readlimit)
```
    Mark the current position.
    
    覆盖:
    
    mark 在类中 Reader
    
    参数:
    
    readlimit - The number of characters before this marked position is invalid.
    
    抛出:
    
    UnsupportedOperationException - if mark is not supported.
  - markSupported
```
public boolean markSupported()
```
    Indicates whether mark is supported.
    
    覆盖:
    
    markSupported 在类中 Reader
    
    返回:
    
    Whether mark is supported or not.
  - read
```
public int read()
         throws IOException
```
    Read a character.
    
    覆盖:
    
    read 在类中 Reader
    
    返回:
    
    Either The character value returned by processChar() or -1 if the end of file has been reached and throwEofException is set to false.
    
    抛出:
    
    EOFException - if the end of file is reached and throwEofException is set to true.
    
    IOException - if trying to read past the end of file.
  - read
```
public int read(char[] chars)
         throws IOException
```
    Read some characters into the specified array.
    
    覆盖:
    
    read 在类中 Reader
    
    参数:
    
    chars - The character array to read into
    
    返回:
    
    The number of characters read or -1 if the end of file has been reached and throwEofException is set to false.
    
    抛出:
    
    EOFException - if the end of file is reached and throwEofException is set to true.
    
    IOException - if trying to read past the end of file.
  - read
```
public int read(char[] chars,
                int offset,
                int length)
         throws IOException
```
    Read the specified number characters into an array.
    
    指定者:
    
    read 在类中 Reader
    
    参数:
    
    chars - The character array to read into.
    
    offset - The offset to start reading characters into.
    
    length - The number of characters to read.
    
    返回:
    
    The number of characters read or -1 if the end of file has been reached and throwEofException is set to false.
    
    抛出:
    
    EOFException - if the end of file is reached and throwEofException is set to true.
    
    IOException - if trying to read past the end of file.
  - reset
```
public void reset()
           throws IOException
```
    Reset the stream to the point when mark was last called.
    
    覆盖:
    
    reset 在类中 Reader
    
    抛出:
    
    UnsupportedOperationException - if mark is not supported.
    
    IOException - If no position has been marked or the read limit has been exceed since the last position was marked.
  - skip
```
public long skip(long numberOfChars)
          throws IOException
```
    Skip a specified number of characters.
    
    覆盖:
    
    skip 在类中 Reader
    
    参数:
    
    numberOfChars - The number of characters to skip.
    
    返回:
    
    The number of characters skipped or -1 if the end of file has been reached and throwEofException is set to false.
    
    抛出:
    
    EOFException - if the end of file is reached and throwEofException is set to true.
    
    IOException - if trying to read past the end of file.
  - processChar
```
protected int processChar()
```
    Return a character value for the read() method.
    This implementation returns zero.
    
    返回:
    
    This implementation always returns zero.
  - processChars
```
protected void processChars(char[] chars,
                            int offset,
                            int length)
```
    Process the characters for the read(char[], offset, length) method.
    This implementation leaves the character array unchanged.
    
    参数:
    
    chars - The character array
    
    offset - The offset to start at.
    
    length - The number of characters.

类 NullReader

字段概要

从类继承的字段 java.io.Reader

构造器概要

方法概要

从类继承的方法 java.io.Reader

从类继承的方法 java.lang.Object

构造器详细资料

NullReader

NullReader

方法详细资料

getPosition

getSize

close

mark

markSupported

read

read

read

reset

skip

processChar

processChars