HeadFilter (Apache Ant API)

org.apache.tools.ant.filters

## Class HeadFilter

- java.lang.Object
- - java.io.Reader
  - - java.io.FilterReader
    - - org.apache.tools.ant.filters.BaseFilterReader
      - - org.apache.tools.ant.filters.BaseParamFilterReader
        - - org.apache.tools.ant.filters.HeadFilter

- All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable, ChainableReader, Parameterizable

      public final class HeadFilter
      extends BaseParamFilterReader
      implements ChainableReader

  Reads the first `n` lines of a stream. (Default is first 10 lines.)

  Example:

      <headfilter lines="3"/>

  Or:

      <filterreader classname="org.apache.tools.ant.filters.HeadFilter">
          <param name="lines" value="3"/>
       </filterreader>

- - ### Field Summary

    - ### Fields inherited from class java.io.FilterReader

      `in`

    - ### Fields inherited from class java.io.Reader

      `lock`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `HeadFilter()` Constructor for "dummy" instances.
    `HeadFilter(java.io.Reader in)` Creates a new filtered reader.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `java.io.Reader` | `chain(java.io.Reader rdr)` Creates a new HeadFilter using the passed in Reader for instantiation.
    `int` | `read()` Returns the next character in the filtered stream.
    `void` | `setLines(long lines)` Sets the number of lines to be returned in the filtered stream.
    `void` | `setSkip(long skip)` Sets the number of lines to be skipped in the filtered stream.

    - ### Methods inherited from class org.apache.tools.ant.filters.BaseParamFilterReader

      `getParameters, setParameters`

    - ### Methods inherited from class org.apache.tools.ant.filters.BaseFilterReader

      `getInitialized, getProject, read, readFully, readLine, setInitialized, setProject, skip`

    - ### Methods inherited from class java.io.FilterReader

      `close, mark, markSupported, ready, reset`

    - ### Methods inherited from class java.io.Reader

      `read, read`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### HeadFilter

          public HeadFilter()

      Constructor for "dummy" instances.
      See Also:
        `BaseFilterReader.BaseFilterReader()`

    - #### HeadFilter

          public HeadFilter(java.io.Reader in)

      Creates a new filtered reader.
      Parameters:
        `in` - A Reader object providing the underlying stream. Must not be `null`.

  - ### Method Detail

    - #### read

          public int read()
                   throws java.io.IOException

      Returns the next character in the filtered stream. If the desired number of lines have already been read, the resulting stream is effectively at an end. Otherwise, the next character from the underlying stream is read and returned.
      Overrides:
        `read` in class `java.io.FilterReader`
      Returns:
        the next character in the resulting stream, or -1 if the end of the resulting stream has been reached
      Throws:
        `java.io.IOException` - if the underlying stream throws an IOException during reading

    - #### setLines

          public void setLines(long lines)

      Sets the number of lines to be returned in the filtered stream.
      Parameters:
        `lines` - the number of lines to be returned in the filtered stream

    - #### setSkip

          public void setSkip(long skip)

      Sets the number of lines to be skipped in the filtered stream.
      Parameters:
        `skip` - the number of lines to be skipped in the filtered stream

    - #### chain

          public java.io.Reader chain(java.io.Reader rdr)

      Creates a new HeadFilter using the passed in Reader for instantiation.
      Specified by:
        `chain` in interface `ChainableReader`
      Parameters:
        `rdr` - A Reader object providing the underlying stream. Must not be `null`.
      Returns:
        a new filter based on this configuration, but filtering the specified reader