Extracting numbers from a string in java

Question

I have a string like this 3x^2 I want to extract the first and the second number and store them in an array. and if they didn't exist they should be considered as 1.

EDIT : For example in string x the first and the second number are 1 or in string 3x the second number is 1. I think it should be clear now.

Can you elaborate on your question by giving a more general expression which you want to process and extract? — Tim Biegeleisen, Mar 10 '16 at 08:32
You are way too vague. what do you mean? numbers separated by a separator, like "1-558-3" or numbers without any separator, like "15583"? if it's the second case, how is the application to know the first number is 1 and not 15, 155, ... ? — Stultuske, Mar 10 '16 at 08:32
in "3x" the second number is 1 ... there is no 1 in that String — Stultuske, Mar 10 '16 at 08:52

score 1 · Answer 1 · answered Mar 10 '16 at 08:32

1

if the numbers are allways separated by x^, just split the string using this separator

String[] splitted = "3x^2".split("x\\^");

answered Mar 10 '16 at 08:32

Raphael Roth

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Nikolas Charalambidis · Accepted Answer · 2016-03-10T08:49:17.933

Just get digits with the Regex:

String str = "3x^2";
String pattern = "(\\d+)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(str);
ArrayList<Integer> numbers = new ArrayList<>();

Find with Matcher all numbers and add them to the ArrayList. Don't forget to convert them to int, because m.group() returns the String.

while (m.find()) {
   numbers.add(Integer.parseInt(m.group()));
}

And if your formula doesn't contain the second number, add there your desired default item.

if (numbers.size<2) {
   numbers.add(1);
}

Finally print it out with:

for (int i: numbers) {
   System.out.print(i + " ");
}

And the output for 3x^2 is 3 2.

And for the 8x it is 8 1.

Extracting numbers from a string in java

2 Answers2