Class 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 Description
      HeadFilter()
      Constructor for "dummy" instances.
      HeadFilter​(java.io.Reader in)
      Creates a new filtered reader.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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 java.io.FilterReader

        close, mark, markSupported, ready, reset
      • Methods inherited from class java.io.Reader

        nullReader, read, read, transferTo
      • 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()
      • 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