Regarding Java String dollar to cents conversion

Question

I have a java string which has an dollar value and cents value after decimal points and starting with a + or - sign. I want to convert into cents and store it in a integer (it can have + or -). Also i need to check if the cents part (after decimal point) not more than 2 digits and throw an error message if exists

example : String dollval= "12.23" output value =1223 cents

String dollval= "12" output value = 1200 cents

String dollval= "-0.09" output value = -9 cents

String dollval= ""-99" output value = -99 cents

String dollval= "-99.0" output value = -99 cents

String dollval= "-99.23" output value =-9923 cents

String dollval="0.00 " output value=0 cents

String dollval="5.2" output val= 520 cents

String dollval = "5.20" output value =520 cents

Answer 1

It's a good homework problem. Try tokenizing (or splitting) on the decimal. The first token will give you your whole dollars. The second part, the pennies. If only 1 character after the decimal, multiply by 10 so that 12.3 becomes 12 * 100 + 3 * 10, not just 3. If more than 2 tokens, error.

You could also do (int) Float.parseFloat(string) * 100, but you might have some rounding problems. Better to stay in integer land.

Answer 2

There are still major problems with your examples.

String dollval= "12" output value = 1200 cents

String dollval= "-99" output value = -99 cents

So if a number is positive it is dollars, and if it is negative it is cents? This is illogical.

String dollval= "-99.0" output value = -99 cents

String dollval= "-99.23" output value =-9923 cents

What do the numbers after the '.' actually mean? In the first example they seem to mean a fractional part of a cent. In the second, they mean a fractional part of a dollar. This is illogical.

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Having said that, I would implement this using a regex to split the input into parts, convert the parts to integers and then reassemble them based on the meaning inferred from the examples. Something like this:

int cents;
Matcher m = Pattern.compile("([-+]?)([0-9]+)(?:\.([0-9]{0,2}))").matcher(input);
if (m.matches()) {
    int sign = m.group(0).equals("-") ? -1 : 1;
    cents = Integer.parseInt(m.group(1));
    if (m.groupCount() == 3) {
        // I'm assuming that "99.1" should mean 9910 cents ...
        int tmp = (m.group(2).length() == 0) ? 0 :
               (m.group(2).length() == 1) ? (Integer.parseInt(m.group(2)) * 10) :
               Integer.parseInt(m.group(2));
        cents = cents * 100 + tmp;
    }
    cents = cents * sign;
} else {
    throw new SomeException("invalid dollars/cents value");
}

Warning: this code may not even compile, let alone work as expected. And of course, the implementation depends on aspects of the requirements ... which I still think are wrong.

Answer 3

I would most definitely not do this with regexps, because that leads to needlessly complex and error-prone code. The Java standard API offers a much simple solution:

    BigDecimal dollars = new BigDecimal(inputString);
    if(dollars.scale()>2)
    {
        throw new IllegalArgumentException();
    }
    int cents = dollars.multiply(new BigDecimal(100)).intValue();

Note though that your requirements above are not consistent:

String dollval= "12" output value = 1200 cents

String dollval= ""-99" output value = -99 cents

My code assumes that this is an error and you meant numbers without a fractional part to be interpreted as full dollars for positive as well as negative numbers.