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:

1. Some lines of code repeat twice.

2. 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?

Solution 1

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”

Solution 2

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.

Solution 3

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)+"  ");
}

Comments

[Juvanis]

you are not allowed to use regex?

[Hovercraft Full Of Eels]

My thoughts exactly as this would be pretty trivial using regular expressions and String#replaceAll(...)

[Dave Newton]

For code reviews please use the code review stack exchange site :)

[Andrea Colleoni]

stackoverflow.com/questions/2367381/…

[Toni]

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]

Yes, it matches. Just add results to some container of your choice.

[user471011]

And what about this line: "123fgfgfgfgfgfgv5kkk60". Expected result is [123, 5, 60].

[scanE]

modified code int len = s.length(); for(int i=0;i<len;i++) { if(Character.isDigit(s.charAt(i))) { System.out.print(s.charAt(i)); i++; while(i<len&&Character.isDigit(s.charAt(i))) { System.out.print(s.charAt(i)); i++; } System.out.print(" "); } }

[Dave Newton]

@user1831612 Edit your answer; don't try to stuff code into a comment--it's illegible.

[Jelle de Fries]

You should put str = str.replaceAll("[^-?0-9]+", " "); to match negative numbers.

[Maxim Shoustin]

@JelledeFries, well, who knows if - represented as minus or hyphen.

[Maxim Shoustin]

@JelledeFries I edited my answer with "-" support if needed

[Jelle de Fries]

@MaximShoustin You are right, it depends on the problem. I had a problem that required the recognition of negative numbers.

[kris123456]

But the above solution doesn't seem to work for "0.0". Any suggestions on how to get this fixed too?

[Maxim Shoustin]

@kris123456 well, 0.0 is not number. suppose u need a pattern something like [^-?0-9]+.[0-9]+