Sort method not working in an attempt to sort a String ArrayList

Question

I'll start by first off saying that my sort must be hard coded. I may not use previously existing sort functions. So i wrote this:

for(int g = 0; g < priceArray.size(); g++)
{
    for(int h = 1; h < priceArray.size() - 1; h++)
    {
        int found = priceArray.get(h).indexOf('$', 8);

        if(Double.parseDouble(priceArray.get(h).substring(found+1)) > Double.parseDouble(priceArray.get(h+1).substring(found+1)))
        {
            String a = priceArray.get(h);
            String b = priceArray.get(h+1);

            priceArray.set(h,b);
            priceArray.set(h+1, a);
        }
    }
}

Earlier on in the code, this code puts input into the ArrayList:

double oneD = daIS.readDouble();
int twoD = (int)daIS.readDouble();
double threeD = oneD * twoD;

String oneT = (String.format("$%.2f", oneD));
String twoT = (String.format("%s", twoD));
String threeT = (String.format("$%.2f", threeD));

priceArray.add(oneT + " x " + twoT + " = " + threeT);

So basically, this code gets input, puts its into the arraylist, and the sort method then searches for the second $ money sign in the array index, and gets the substring so that it copies the money amount after the $ symbol. Parses it to double and compares it to the next index (h+1).

If index h is larger than index h+1, we switch the two. And the loops keep going. Eventually, in code i didn't post, the code is displayed in a new window in sorted order.

Example: I open program, input 5 and input 3 in spinner. If i press save, these are saved in my binary file and later converted back into the arraylist. I press retrieve and my output is

$5.00 x 3 = $15.00

This works perfectly fine if i input

10 and 5(spinner)
20 and 2
50 and 1
30 and 4

as the output is

$20.00 x 2 = $40.00
$10.00 x 5 = $50.00
$50.00 x 1 = $50.00
$30.00 x 4 = $120.00

but if my input is something like

10 x 1(spinner)
100 x 1
10 x 1

the program breaks and returns

Exception in thread "JavaFX Application Thread"
java.lang.NumberFormatException: For input string: "$100.00"
    at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source)
    at sun.misc.FloatingDecimal.parseDouble(Unknown Source)
    at java.lang.Double.parseDouble(Unknown Source)

I know this is quite confusing and maybe you question the necessity of my hard-coded string sort, but it's a requirement sadly. And works up to a point, so i believe it should be fixable. Thanks for reading.

EDIT: Solution with assistance of @Nabin Bhandari

int found1 = priceArray.get(h).lastIndexOf('$');
int found2 = priceArray.get(h+1).lastIndexOf('$');

if(Double.parseDouble(priceArray.get(h).substring(found1+1)) > Double.parseDouble(priceArray.get(h+1).substring(found2+1)))

For some reason you're looking for where is the $ sign using indexOf() rather than just skipping the first character assuming that this is the $ sign. But you do it with one of the elements you compare, the other one you just assume it has the $ sign at the same place. That sounds inconsistent: if you know that your items all have consistent $ sign position, then you have no need to look for it with indexOf(). Look at the line that describes your NumberFormatException: it hints to you that you're trying to parse as a number something that starts with $. Not good. — kumesana
– kumesana, Commented Oct 5, 2017 at 16:13
@kumesana the "if blah > blah" line is the error line. When searchinf ro the '$' sign, i put index 8 as part of the indexOf, forcing it to start searching after a certain amoutn of characters. Though realistically, as long as it starts after the first character, which is a $ sign, it shouldnt affect it. The position of the $ sign cannot be consistent as larger inputs will shift around the length of the string. I did see that it was trying to parse the $ sign, but it shouldn't be, as i coded 'found+1' which retrieves the character after the $ sign. I might need to play around with numbers — Lumi
– Lumi, Commented Oct 5, 2017 at 16:22

Nabin Bhandari · Accepted Answer · 2017-10-05 18:15:09Z

1

In your code:

int found = priceArray.get(h).indexOf('$', 8);

You are using this value for both priceArray.get(h) and priceArray.get(h+1).

Instead of that you should get two different indices for two different prices.

for(int g = 0; g < priceArray.size(); g++)
{
    for(int h = 1; h < priceArray.size() - 1; h++)
    {
        int found1 = priceArray.get(h).lastIndexOf('$');
        int found2 = priceArray.get(h+1).lastIndexOf('$');

        String firstPrice = priceArray.get(h);
        String secondPrice = priceArray.get(h+1);

        String first = firstPrice.substring(found1+1);
        String second = secondPrice.substring(found2+1);

        if(Double.parseDouble(first) > Double.parseDouble(second))
        {
            String a = priceArray.get(h);
            String b = priceArray.get(h+1);

            priceArray.set(h,b);
            priceArray.set(h+1, a);
        }
    }
}

But the above code do not seem to sort the prices.

So here's an alternative way to sort the list:

Collections.sort(priceArray, new Comparator<String>() {
    @Override
    public int compare(String p1, String p2) {
        String first = p1.substring(p1.lastIndexOf('$')+1);
        String second = p2.substring(p2.lastIndexOf('$')+1);
        System.out.println(first);
        System.out.println(second);
        return (int) (Double.parseDouble(first)-Double.parseDouble(second));
    }
});

edited Oct 5, 2017 at 18:15

answered Oct 5, 2017 at 16:13

Nabin Bhandari

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5 Comments

Lumi Over a year ago

Your code isn't comparing anything. No sort. My program runs just fine with a single set of inputs as nothing is being sorted.

Nabin Bhandari Over a year ago

But the logic of parsing is pretty much the same. I just rewrote your code. Can you post your whole code?

Lumi Over a year ago

link to code

Lumi Over a year ago

My man! I looked at your code and quickly realized that you are indeed correct, i need a found1 and found2. I took your earlier lastindexof idea and added int found1 = priceArray.get(h).lastIndexOf('$'); and int found2 = priceArray.get(h+1).lastIndexOf('$'); Edited my if statement to contain the found1+1 and found2+1. Ran the code and it works beautifully. Thank you for taking the time to figure this out! I really appreciate it.

Nabin Bhandari Over a year ago

Glad I could help. Sometimes mistakes happen. Good luck.

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