Java string -> two numbers

Question

The operation I'm hoping to perform is to go from:

String "32.63578..."

to:

float 32.63
long 578... //where '...' is rest of string

Something like the following in Python:

split = str.find('.')+2
float = str[:split]
long = str[split:]

I'm new to Java, so I began by trying to look up equivalents, however it seems like a more convoluted solution than perhaps a regex would be? Unless there's more similar functions to python than splitting into a char array, and repeatedly iterating over?

see java.substring method.. Then Float.parseFloat and Long.parseLong method — stinepike, Feb 26 '14 at 04:34
@StinePike `substring` doesn't help, I don't know the index, need to 'find' the decimal point. — OJFord, Feb 26 '14 at 04:36
I strongly recommend learning to use Javadocs. But the methods you need are `indexOf` and `substring`. — Dawood ibn Kareem, Feb 26 '14 at 04:37
refer http://stackoverflow.com/questions/14833008/java-string-split-with-dot and then use Float.parseFloat and Long.parseLong as @StinePike mentioned — Mobin Skariya, Feb 26 '14 at 04:40
What are you *really* trying to do, here? I can't think of a reason to split a number like this. — David Ehrmann, Feb 26 '14 at 05:00
Yeah, I've seen plenty of cases of file formats involving fixed-width fields without separators, where you split what _looks like_ one number, at a particular position, because it's really two numbers. Less common these days, but 20 years ago, this would have been quite a normal thing to want to do. — Dawood ibn Kareem, Feb 26 '14 at 05:22
@OllieFord fair enough, but why no delimiter? It seems rather brittle this way. — David Ehrmann, Feb 26 '14 at 05:22
@DavidWallace I'd rather at least have a struct with two big-endian values, then. Or a float and a varint. Data can be stored more efficiently. — David Ehrmann, Feb 26 '14 at 05:25
I'm guessing, here, but it looks like you *actually* want a BigDecimal. — David Ehrmann, Feb 26 '14 at 04:36
I'm guessing too, but I don't think so. They're separate numbers, unrelated, being read from a string. — OJFord, Feb 26 '14 at 04:37
@OllieFord Why do you have two unrelated numbers that aren't delimited in a string? It sounds like a headache to work with. — David Ehrmann, Feb 26 '14 at 04:38
If the OP wants exactly 32.63 (with that scale) then that's what he is going to need. — Bhesh Gurung, Feb 26 '14 at 04:42
@BheshGurung - it is unclear how many digits the second number has... — Floris, Feb 26 '14 at 04:50

falsetru · Accepted Answer · 2014-02-26T04:51:57.360

5

Use indexOf and substring methods:

String str = "32.63578";
int i = str.indexOf(".") + 3;
String part1 = str.substring(0, i);     // "32.63"
String part2 = str.substring(i);        // "578"

float num1 = Float.parseFloat(part1);   // 32.63
long num2 = Long.parseLong(part2);      // 578

edited Feb 26 '14 at 04:51

answered Feb 26 '14 at 04:40

falsetru

357,413
63
732
636

Yes. And then convert these strings to the numerical type desired. – Floris Feb 26 '14 at 04:42
1

@Floris, I added convert part. Thank you for comment. – falsetru Feb 26 '14 at 04:43
@falsetru happy to help make a good-ish answer good enough to get my vote! – Floris Feb 26 '14 at 04:51
If you're going to give two answers, you should really give them as two separate answers. Someone may wish to upvote one and downvote the other. – Dawood ibn Kareem Feb 26 '14 at 04:53
@DavidWallace, I see. deleted the regular expression alternative. – falsetru Feb 26 '14 at 04:55
Why don't you post it as a second answer? You're allowed! And someone may learn something from it, which is kind of the point of Stack Overflow. – Dawood ibn Kareem Feb 26 '14 at 04:57
@DavidWallace, added the regular expression alternative as separated answer. – falsetru Feb 26 '14 at 05:03

score 1 · Answer 2 · answered Feb 26 '14 at 05:02

Regular expression alternative:

String str = "32.63578";
String[] parts = str.split("(?<=\\.\\d{2})");
System.out.println(parts[0]); // "32.63"
System.out.println(parts[1]); // "578"

About the regular expression used:

(?<=\.\d{2})

It's positive lookbehind (?<=...). It matches at the position where is preceded by . and 2 digits.

score 0 · Answer 3 · edited Feb 26 '14 at 04:47

0

You can use the split method in String if you want to cleanly break the two parts.

However, if you want to have trailing decimals like in your example, you'll probably want to do something like this:

String str = "32.63578...";
String substr1, substr2;

for (int i = 0; i < str.length(); i++)
{
  if (str.charAt(i) == '.')
  {
    substr1 = str.substring(0, i + 3);
    substr2 = str.substring(i + 3, str.length());
    break;
  }
}

//convert substr1 and substr2 here

edited Feb 26 '14 at 04:47

Mobin Skariya

392
3
12

answered Feb 26 '14 at 04:39

yossarian

1,537
14
21

1

@Floris are you sure? – Dawood ibn Kareem Feb 26 '14 at 04:54
@Floris it's cleaner, but the efficiency is probably exactly the same. After all, getting the index of a character means looping somehow. – yossarian Feb 26 '14 at 04:55
1

@DavidWallace - Maybe not in execution time, but in number of characters used. I think it is good practice to use a function when it is "just right" for the job. – Floris Feb 26 '14 at 05:16
I agree that it's good practice not to do what this respondent has done. I just can't see that it's less efficient than using `indexOf`. – Dawood ibn Kareem Feb 26 '14 at 05:20

score 0 · Answer 4 · answered Feb 26 '14 at 05:23

String s ="32.63578";
    Pattern pattern = Pattern.compile("(?<Start>\\d{1,10}.\\d{1,2})(?<End>\\d{1,10})");
    Matcher match = pattern.matcher(s);
    if (match.find()) {
        String start = match.group("Start");
        String ending = match.group("End");
        System.out.println(start);
        System.out.println(ending);
    }

Java string -> two numbers

4 Answers4