no of common characters between two strings in java

// Java program to print common characters 
// of two Strings in alphabetical order 
import java.io.*; 
import java.util.*; 
  
// Function to find similar characters 
public class Simstrings 
{ 
    static final int MAX_CHAR = 26; 
  
    static void printCommon(String s1, String s2) 
    { 
       // two arrays of length 26 to store occurrence 
        // of a letters alphabetically for each string 
        int[] a1 = new int[MAX_CHAR]; 
        int[] a2 = new int[MAX_CHAR]; 
  
        int length1 = s1.length(); 
        int length2 = s2.length(); 
  
        for (int i = 0 ; i < length1 ; i++) 
           a1[s1.charAt(i) - 'a'] += 1; 
  
        for (int i = 0 ; i < length2 ; i++) 
           a2[s2.charAt(i) - 'a'] += 1; 
  
        // If a common index is non-zero, it means 
        // that the letter corresponding to that 
        // index is common to both strings 
        for (int i = 0 ; i < MAX_CHAR ; i++) 
        { 
            if (a1[i] != 0 && a2[i] != 0) 
            { 
                // Find the minimum of the occurrence 
                // of the character in both strings and print 
                // the letter that many number of times 
                for (int j = 0 ; j < Math.min(a1[i], a2[i]) ; j++) 
                    System.out.print(((char)(i + 'a'))); 
            } 
        } 
    } 
  
    // Driver code 
    public static void main(String[] args) throws IOException 
    { 
        String s1 = "geeksforgeeks", s2 = "practiceforgeeks"; 
        printCommon(s1, s2); 
    } 
}