Find all numbers in the String

Question

For example, I have input String: "qwerty1qwerty2";

As Output I would like have [1,2].

My current implementation below:

import java.util.ArrayList;
import java.util.List;

public class Test1 {

    public static void main(String[] args) {
        String inputString = args[0];
        String digitStr = "";
        List<Integer> digits = new ArrayList<Integer>();

        for (int i = 0; i < inputString.length(); i++) {
            if (Character.isDigit(inputString.charAt(i))) {
                digitStr += inputString.charAt(i);
            } else {
                if (!digitStr.isEmpty()) {
                    digits.add(Integer.parseInt(digitStr));
                    digitStr = "";
                }
            }
        }
        if (!digitStr.isEmpty()) {
            digits.add(Integer.parseInt(digitStr));
            digitStr = "";
        }

        for (Integer i : digits) {
            System.out.println(i);
        }
    }
}

But after double check I dislake couple points:

Some lines of code repeat twice.
I use List. I think it is not very good idea, better using array.

So, What do you think?

Could you please provide any advice?

My thoughts exactly as this would be pretty trivial using regular expressions and `String#replaceAll(...)` — Hovercraft Full Of Eels, Nov 18 '12 at 13:22
For code reviews please use the code review stack exchange site :) — Dave Newton, Nov 18 '12 at 13:26
http://stackoverflow.com/questions/2367381/extract-numbers-from-a-string-java — Andrea Colleoni, Nov 18 '12 at 13:27

score 69 · Accepted Answer · edited Apr 28 '21 at 20:51

69

Use replaceAll:

String str = "qwerty1qwerty2";      
str = str.replaceAll("[^0-9]+", " ");
System.out.println(Arrays.asList(str.trim().split(" ")));

Output:

[1, 2]

[EDIT]

If you want to include - a.e minus, add -?:

String str = "qwerty-1qwerty-2 455 f0gfg 4";      
str = str.replaceAll("[^-?0-9]+", " "); 
System.out.println(Arrays.asList(str.trim().split(" ")));

Output:

[-1, -2, 455, 0, 4]

Description

[^-?0-9]+

+ Between one and unlimited times, as many times as possible, giving back as needed
-? One of the characters “-?”
0-9 A character in the range between “0” and “9”

edited Apr 28 '21 at 20:51

Spectric

30,714
6
20
43

answered Nov 18 '12 at 13:34

Maxim Shoustin

77,483
27
203
225

1

You should put `str = str.replaceAll("[^-?0-9]+", " ");` to match negative numbers. – Jelle de Fries Sep 04 '14 at 10:44
@JelledeFries, well, who knows if `-` represented as *minus* or *hyphen*. – Maxim Shoustin Sep 04 '14 at 11:26
1

@JelledeFries I edited my answer with "-" support if needed – Maxim Shoustin Sep 05 '14 at 06:37
@MaximShoustin You are right, it depends on the problem. I had a problem that required the recognition of negative numbers. – Jelle de Fries Sep 08 '14 at 10:57
But the above solution doesn't seem to work for "0.0". Any suggestions on how to get this fixed too? – kris123456 Jan 12 '15 at 07:47
@kris123456 well, 0.0 is not number. suppose u need a pattern something like `[^-?0-9]+.[0-9]+` – Maxim Shoustin Jan 12 '15 at 08:14

score 6 · Answer 2 · answered Nov 18 '12 at 13:27

6

import java.util.regex.Matcher;
import java.util.regex.Pattern;

...

Pattern pattern = Pattern.compile("[0-9]+"); 
Matcher matcher = pattern.matcher("test1string1337thingie");

// Find all matches
while (matcher.find()) { 
  // Get the matching string  
  String match = matcher.group();
}

Is one regexp solution.

answered Nov 18 '12 at 13:27

Toni

273
3
10

Actually, let me check if the pattern is correct usage here, just quickly googled and improvised. Haven't used java nor regexp in a while. – Toni Nov 18 '12 at 13:29
Yes, it matches. Just add results to some container of your choice. – Toni Nov 18 '12 at 13:49

score 2 · Answer 3 · answered Nov 18 '12 at 13:55

2

try this code

String s = "qwerty1qwerty2";
for(int i=0;i<s.length();i++)
{
   if(Character.isDigit(s.charAt(i)))
   System.out.print(s.charAt(i)+"  ");
}

answered Nov 18 '12 at 13:55

scanE

332
4
19

And what about this line: "123fgfgfgfgfgfgv5kkk60". Expected result is [123, 5, 60]. – user471011 Nov 18 '12 at 14:01
modified code int len = s.length(); for(int i=0;i – scanE Nov 19 '12 at 05:14
1

@user1831612 Edit your answer; don't try to stuff code into a comment--it's illegible. – Dave Newton Nov 28 '12 at 05:01

Find all numbers in the String

3 Answers3

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