org.sadun.util
Class PushbackReader

java.lang.Object
  java.io.Reader
      java.io.FilterReader
          org.sadun.util.PushbackReader

public class PushbackReader

extends java.io.FilterReader

A reader that allows to push back an arbitrary number of characters.

It also offers some commonly used lookahead comparison operations (based on reading/unreading characters). These should really be in a separate class in the future.

Version:

1.1

Author:

Cristiano Sadun

Field Summary

Fields inherited from class java.io.FilterReader

in

Fields inherited from class java.io.Reader

lock

Constructor Summary

PushbackReader(java.io.Reader r)
Create a pushback reader over the given source of characters, allowing to push

Method Summary

static void	main(java.lang.String[] args)
boolean	nextEquals(java.lang.String s) Looks ahead to check whether the next characters on the stream equal the given String.
boolean	nextEquals(java.lang.String s, boolean unreadIfTrue) Looks ahead to check whether the next characters on the stream equal the given String.
boolean	nextEqualsIgnoreCase(java.lang.String s, boolean unreadIfTrue) Looks ahead to check whether the next characters on the stream equal the given String (ignoring letter case).
int	read() Read the next character.
java.lang.String	readNext(int n) Attempt to read the next n characters in the stream, then unread them.
void	unread(int c) Unread the given character.

Methods inherited from class java.io.FilterReader

close, mark, markSupported, read, ready, reset, skip

Methods inherited from class java.io.Reader

read

Methods inherited from class java.lang.Object

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

Constructor Detail

PushbackReader

public PushbackReader(java.io.Reader r)

Create a pushback reader over the given source of characters, allowing to push

Parameters:

r - the source of characters

Method Detail

read

public int read()
         throws java.io.IOException

Read the next character.

Returns:

the next character on the stream, or -1 at EOF

Throws:

java.io.IOException - if there is a problem reading the stream.

unread

public void unread(int c)
            throws java.io.IOException

Unread the given character. The character will be returned as result of the next read() operation.

Parameters:

c - the charater to unread

Throws:

java.io.IOException - if there is a problem unreading the character.

readNext

public java.lang.String readNext(int n)
                          throws java.io.IOException

Attempt to read the next n characters in the stream, then unread them.

Parameters:

n - the number of character to read.

Returns:

a string with the read characters. Note that the string may contain less than n characters if EOF was reached.

Throws:

java.io.IOException - in case of problems reading the stream

nextEquals

public boolean nextEquals(java.lang.String s)
                   throws java.io.IOException

Looks ahead to check whether the next characters on the stream equal the given String. The reader stream position is unchanged.

Parameters:

s - the string to compare

Returns:

true if the stream contains the string at the current position

Throws:

java.io.IOException - in case of problems reading the stream

nextEquals

public boolean nextEquals(java.lang.String s,
                          boolean unreadIfTrue)
                   throws java.io.IOException

Looks ahead to check whether the next characters on the stream equal the given String. The reader stream position is unchanged if there is no match. If a match exists, it is changed or not depending on the value of the unreadIfTrue parameter.

Parameters:

s - the string to compare

unreadIfTrue - if false and the comparison is successful, the stream position will be after the successfully compared string. Otherwise, it will be unchanged.

Returns:

true if the stream contains the string at the current position

Throws:

java.io.IOException - in case of problems reading the stream

nextEqualsIgnoreCase

public boolean nextEqualsIgnoreCase(java.lang.String s,
                                    boolean unreadIfTrue)
                             throws java.io.IOException

Looks ahead to check whether the next characters on the stream equal the given String (ignoring letter case). The reader stream position is unchanged if there is no match. If a match exists, it is changed or not depending on the value of the unreadIfTrue parameter.

Parameters:

s - the string to compare

unreadIfTrue - if false and the comparison is successful, the stream position will be after the successfully compared string. Otherwise, it will be unchanged.

Returns:

true if the stream contains the string at the current position

Throws:

java.io.IOException - in case of problems reading the stream

main

public static void main(java.lang.String[] args)
                 throws java.lang.Exception

Throws:

java.lang.Exception