import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public final class Start {
    public static void main(final String[] args) {

        final String str = "abcdefg";
        final List<Character> list = IntStream.range(0, str.length()).mapToObj(i -> str.charAt(i)).collect(Collectors.toList());
        System.out.println(list.indexOf('a')); // 0
        System.out.println(list.indexOf('b')); // 1
    }
}