private final Token first;

private Token current;

public JavaTokenizer(String image) {

first = parse(image);

current = first;

}

@Override

public Token firstToken() {

current = first;

return current;

}

@Override

public Token nextToken() {

if (current.next != null)

return current = current.next;

return null;

}

@Override

public Token getToken(int index) {

Token result = current;

for (int i = 0; i < index && result != null; i++)

result = result.next;

return result;

}

@Override

public void skip(int count) {

int n = count;

while (n-- > 0 && current != null)

current = current.next;

}

private static Token parse(String image) {

int position = 0;

final int length = image.length();

while (position < length) {

final char character = image.charAt(position);

if (character == ' ' || character == '\r' || character == '\t' || character == '\n' || character == '\f') {

position++;

} else

break;

}

final String tmp = image.substring(position);

for (TokenType type : TokenType.values()) {

Matcher matcher = type.r.matcher(tmp);

if (matcher.find()) {

final String tokenImage = matcher.group(1);

return new Token(tokenImage, type, parse(tmp.substring(tokenImage.length())));

}

}

return null;

}