Class TokenScanner

java.lang.Object

TokenScanner

All Implemented Interfaces:

java.util.Iterator<java.lang.String>

public class TokenScanner
extends java.lang.Object
implements java.util.Iterator<java.lang.String>

Provides a token Iterator for a given Reader.

Hint: See the code for WordScanner from lecture for inspiration/help. We very strongly discourage copying any of that code for use here. The job of TokenScanner is not the same as that of WordScanner; any attempts to force WordScanner code to directly work for this class will likely cause more headaches than help.

Constructor Summary

Constructors

Constructor and Description
TokenScanner(java.io.Reader in) Creates a TokenScanner for the argued Reader.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	hasNext() Determines whether there is another token available.
static boolean	isWord(java.lang.String s) Determines whether the argued String is a valid word
static boolean	isWordCharacter(int c) Determines whether the argued character is a valid word character.
java.lang.String	next() Returns the next token, or throws a NoSuchElementException if none remain.
void	remove() We don't support this functionality with TokenScanner, but since the method is required when implementing Iterator, we just throw new UnsupportedOperationException();

Methods inherited from class java.lang.Object

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

Constructor Detail

TokenScanner

public TokenScanner(java.io.Reader in)
             throws java.io.IOException

Creates a TokenScanner for the argued Reader.

As an Iterator, the TokenScanner should only read from the Reader as much as is necessary to determine hasNext() and next(). The TokenScanner should NOT read the entire stream and compute all of the tokens in advance.

Parameters:

in - The source Reader for character data

Throws:

java.io.IOException - If there is an error in reading

java.lang.IllegalArgumentException - If the argued Reader is null

Method Detail

isWordCharacter

public static boolean isWordCharacter(int c)

Determines whether the argued character is a valid word character.

Valid word characters are letters (according to Character.isLetter) and apostrophes (which are single quotes '\'').

Parameters:

c - The character to check

Returns:

True if the character is a word character

isWord

public static boolean isWord(java.lang.String s)

Determines whether the argued String is a valid word

A valid word is any sequence of only letter (see Character.isLetter) and/or apostrophe characters. Strings that are null or empty are not valid words.

Parameters:

s - The string to check

Returns:

True if the String is a word

hasNext

public boolean hasNext()

Determines whether there is another token available.

Specified by:

hasNext in interface java.util.Iterator<java.lang.String>

Returns:

True if there is another token available

next

public java.lang.String next()

Returns the next token, or throws a NoSuchElementException if none remain.

Specified by:

next in interface java.util.Iterator<java.lang.String>

Returns:

The next token if one exists

Throws:

NoSuchElementException - When the end of stream is reached

remove

public void remove()

We don't support this functionality with TokenScanner, but since the method is required when implementing Iterator, we just throw new UnsupportedOperationException();

Specified by:

remove in interface java.util.Iterator<java.lang.String>

Throws:

java.lang.UnsupportedOperationException - Since we do not support this functionality