Convert Java Code to Swift : I wanna convert java code to swift facing an issue . Any help is appreciated . 

Java Code : 

 for(String s: str){
          char arr[] = new char[26]

            for(int i =0;i< s.length(); i++){
                arr[s.charAt(i) -'a']++;
            }
}

Swift Code : 

Below are extenions and classes.

    extension String {
        var asciiArray: [UInt32] {
            return unicodeScalars.filter{$0.isASCII}.map{$0.value}
        }
    }
    extension Character {
        var asciiValue: UInt32? {
            return String(self).unicodeScalars.filter{$0.isASCII}.first?.value
        }
    }


    class GroupXXX{
       
        func groupXXX(strList: [String]){
            
            for str in strList{
                
            var charArray = [Character?](repeating: nil, count: 26)
            var s = str.characters.map { $0 }
            
            for i in 0..<s.count{
                charArray[(s[i].asciiValue)! - ('a'.asciiValue)!]++
            }
    
            }
            
        }
    }


