I have a fault in the functions of net help

[bassam123444]

I have a fault in the functions of net help I have a fault in the functions of net help I have a fault in the functions of net help

package jscl.text;

import java.util.Arrays; import java.util.Collections; import java.util.List;

import javax.annotation.Nonnull; import javax.annotation.Nullable;

import jscl.math.Generic; import jscl.text.msg.Messages;

public class Identifier implements Parser {

public static final Parser<String> parser = new Identifier();
private final static List<Character> allowedCharacters = Arrays.asList  ( '√' , '∞', 'π', '∂', '∏', 'Σ', '∫') ;

private Identifier(){}

private static boolean isValidFirstCharacter(char ch) {
    return Character.isLetter(ch) || allowedCharacters.contains(ch);
}

private static boolean isValidNotFirstCharacter(@Nonnull String string, @Nonnull MutableInt position) {
    final char ch = string.charAt(position.intValue());
    return Character.isLetter(ch) || Character.isDigit(ch) || ch == '_';
}

// returns getVariable/constant getName
@Nonnull
public String parse(@Nonnull Parameters p, @Nullable Generic previousSumElement) throws ParseException {
    int pos0 = p.position.intValue();

    ParserUtils.skipWhitespaces(p);

    final StringBuilder result;
    if (p.position.intValue() < p.expression.length() && isValidFirstCharacter(p.expression.charAt(p.position.intValue()))) {
        result = new StringBuilder();
        result.append(p.expression.charAt(p.position.intValue()));
        p.position.increment();
    } else {
        throw ParserUtils.makeParseException(p, pos0, Messages.msg_5);
    }

    while (p.position.intValue() < p.expression.length() && isValidNotFirstCharacter(p.expression, p.position)) {
        result.append(p.expression.charAt(p.position.intValue()));
        p.position.increment();
    }

    return result.toString();
}

}