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

12 Apr, 2022
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
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:
Initialize MAX = 0Run 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.Return MAX at the last.
Initialize MAX = 0
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.
If number greater than MAX, update MAX to number.
Return MAX at the last.
Java
// 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
// 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 BigInteger            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 write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
sumitgumber28
java-regular-expression
Strings
Strings
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.
Comments
Old Comments
Python program to check if a string is palindrome or not
Check for Balanced Brackets in an expression (well-formedness) using Stack
KMP Algorithm for Pattern Searching
Different methods to reverse a string in C/C++
Convert string to char array in C++
Array of Strings in C++ (5 Different Ways to Create)
Longest Palindromic Substring | Set 1
Reverse words in a given string
Caesar Cipher in Cryptography
Length of the longest substring without repeating characters