com.perdues
Class TextFilter

java.lang.Object
  |
  +--com.perdues.TextFilter

public abstract class TextFilter

extends java.lang.Object

Abstract class that provides a framework for programs that filter textual input to an output. Subclass it and define handleLine(String) and a main program to make a complete command-line application.

Field Summary

protected java.io.PrintWriter

w This variable supports output.

Constructor Summary

TextFilter()

Method Summary

void	filter(java.io.File in, java.io.File out) This method opens up a BufferedReader for input from the given input file and a PrintWriter for output to the given output file.
void	filter(java.lang.String[] args) Convenience method that calls the filter method with File arguments.
void	handleEOF() Override this method to define an action to do at end of input.
abstract void	handleLine(java.lang.String line) Filter calls this on each line of input.

Methods inherited from class java.lang.Object

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

Field Detail

w

protected java.io.PrintWriter w

This variable supports output. If the output file is non-null, it will be open to that file. If the output file is null, this will be open to System.out.

Constructor Detail

TextFilter

public TextFilter()

Method Detail

filter

public void filter(java.lang.String[] args)
            throws java.io.IOException

Convenience method that calls the filter method with File arguments. If there are no arguments or the first argument is "-", the input is System.in. If there are not two arguments, the output is System.out. Otherwise input and output are the files named by the first two elements of the args array.

filter

public void filter(java.io.File in,
                   java.io.File out)
            throws java.io.IOException

This method opens up a BufferedReader for input from the given input file and a PrintWriter for output to the given output file. If the input file is null, it uses System.in instead. If the output file is null, this uses System.out in its place.

This reads lines from input until end of file. On each line it calls handleLine, passing it the current line. On end of file or if it catches an exception it closes its input and output files, except it will not close System.in or System.out.

Since reading of lines is done by BufferedReader.readLine, there is no detection of an unterminated last input line.

handleLine

public abstract void handleLine(java.lang.String line)

Filter calls this on each line of input. This method handles the line, for example writing out the transformed input.

handleEOF

public void handleEOF()

Override this method to define an action to do at end of input. This should not close the input or output.