greatest common divisor of strings

 Greatest Common Divisor of Strings

class Solution {
    public String gcdOfStrings(String str1, String str2) {
        if (!(str1+str2).equals(str2+str1)) 
        { 
            return "";
        }
        int a=str1.length();
        int b=str2.length();
        int gcd=1;
        int min=Math.min(a,b);
        for(int i=2;i<=min;i++){
            if(a%i==0 && b%i==0){
                gcd=i;
            }
        }
        return str2.substring(0,gcd);
    }
}