com.hd.stringcalculator.StringCalculator.java Source code

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Here is the source code for com.hd.stringcalculator.StringCalculator.java

Source

/*
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package com.hd.stringcalculator;

import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;
import org.apache.commons.lang.StringUtils;

/**
 *
 * @author Horvth Dniel
 */
public class StringCalculator {

    private final static String DEFAULT_SEPARATOR = ",";
    private String separator;

    public StringCalculator() {
        this(DEFAULT_SEPARATOR);
    }

    public StringCalculator(String separator) {
        this.separator = separator;
    }

    public int add(String numbers) throws NegativeNumberException {
        if (numbers == null) {
            throw new NullPointerException();
        } else if (numbers.isEmpty()) {
            return 0;
        }

        if (!numbers.matches(
                "-?[0-9]+((" + Pattern.quote(separator) + ")-?[0-9]+)*(" + Pattern.quote(separator) + ")?")) {
            throw new IllegalArgumentException("Bad character(s) in input string: " + numbers);
        }

        List<String> numbersList = Arrays
                .asList(numbers.split("(?<!" + Pattern.quote(separator) + ")" + Pattern.quote(separator)));
        List<String> negativeNumbers = new StringListFilter("[-][0-9]+").filter(numbersList);

        if (negativeNumbers.size() > 0) {
            throw new NegativeNumberException(StringUtils.join(negativeNumbers.iterator(), ", "));
        }

        int sum = 0;
        for (String stringNumber : numbersList) {
            sum += Integer.valueOf(stringNumber);
        }

        return sum;
    }

    public String getSeparator() {
        return separator;
    }

    public void setSeparator(String separator) {
        this.separator = separator;
    }
}