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 the WordScanner from Lecture.

Constructor Summary

Constructors

Constructor and Description
TokenScanner(java.io.Reader in) Creates a TokenScanner for a given 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 a given String is a valid word
static boolean	isWordCharacter(int c) Determines whether a given 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 if 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 a given Reader.

As an Iterator, the TokenScanner should only read from the Reader as much as is necessary to determine getNext() 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 - when the provided Reader is null

Method Detail

isWordCharacter

public static boolean isWordCharacter(int c)

Determines whether a given character is a valid word character.

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

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 a given String is a valid word

Valid words are not null or the empty string. They only contain word characters.

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>

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>

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 if 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