Extract maximum numeric value from a given string | Set 2 (Regex approach)

Given an alphanumeric string, extract maximum numeric value from that string.

Examples:

Input : 100klh564abc365bg
Output : 564
Maximum numeric value among 100, 564
and 365 is 564.
Input : abchsd0365sdhs
Output : 365

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

In Set 1, we have discussed general approach for extract numeric value from given string.In this post, we will discuss regular expression approach for same.

Below is one of the regular expression for at least one numeric digit.

\d+

So Regex solution is simple:

1. Initialize MAX = 0
2. Run loop over matcher, whenever match found, convert numeric string to integer and compare it with MAX.
• If number greater than MAX, update MAX to number.
3. Return MAX at the last.

 // Java regex program to extract the maximum value    import java.util.regex.Matcher; import java.util.regex.Pattern;    class GFG  {     // Method to extract the maximum value     static int extractMaximum(String str)     {         // regular expression for atleast one numeric digit         String regex = "\\d+";                    // compiling regex         Pattern p = Pattern.compile(regex);                    // Matcher object         Matcher m = p.matcher(str);                    // initialize MAX = 0         int MAX = 0;                    // loop over matcher         while(m.find())         {             // convert numeric string to integer             int num = Integer.parseInt(m.group());                            // compare num with MAX, update MAX if num > MAX             if(num > MAX)                 MAX = num;         }                     return MAX;         }        public static void main (String[] args)     {         String str = "100klh564abc365bg";                    System.out.println(extractMaximum(str));     } }

Output:

564

But above program wouldn’t work if number is greater that integer range. You can try parseLong() method for numbers upto long range.But to handle the case of large numbers(greater than long range) we can take help of BigInteger class in java. Below is the java program to demonstrate the same.

 // Java regex program to extract the maximum value // in case of large numbers    import java.math.BigInteger; import java.util.regex.Matcher; import java.util.regex.Pattern;    class GFG  {     // Method to extract the maximum value     static BigInteger extractMaximum(String str)     {         // regular expression for atleast one numeric digit         String regex = "\\d+";                    // compiling regex         Pattern p = Pattern.compile(regex);                    // Matcher object         Matcher m = p.matcher(str);                    // initialize MAX = 0         BigInteger MAX = BigInteger.ZERO;                    // loop over matcher         while(m.find())         {             // convert numeric string to BigIntegr             BigInteger num = new BigInteger(m.group());                            // compare num with MAX, update MAX if num > MAX             if(num.compareTo(MAX) > 0)                 MAX = num;         }                     return MAX;         }        public static void main (String[] args)     {         String str = "100klh564231315151313151315abc365bg";                    System.out.println(extractMaximum(str));     } }

Output:

564231315151313151315

This article is contributed by Gaurav Miglani. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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