Daniel Lawson Chapter 4 Self Check 20-28 even

/**
 * Created by Daniel on 4/20/2016.
 */
20.
it prints all the letters in a range of two letters
efg
nopqrs

qr

21.
String s = [words]
char s = s.charAt(0);
if(isUpperCase(c)){
//statements
}
22.
It uses the incorrect syntax of s.charAt(i).toLowerCase(), when it should be:
Character.toLowerCase(s.charAt(i))
24.
/**
 * Created by Daniel on 4/20/2016.
 */
//create a code to examine astring and determine how many of its letters come from the second half of the alhabet
// have values of 'n' or subsequent letters, assume every character in a string is a letter, case intensively
import java.util.*;
public class selfCheck24 {
    public static void main(String[] args) {
        Scanner c = new Scanner(System.in);
        v(c);
    }

    public static void v(Scanner c) {
        System.out.print("Enter a string:");
        String s = c.next();
        int count = 0;
        for (int i = 0; i < s.length(); i++) {
            if (Character.toLowerCase(s.charAt(i)) >= 'n') {
                count++;
            }
        }
        System.out.printf("total count %d",count);
    }
}
26.
In the parameters of the method one must enter the grade percentage value
so that later in the method it can convert the previously gien values to a value between 0.0-4.0
28.
modified version to work in the situation that a != 0... because if a = 0 then you would not be using a quadratic.
 public static String quadratic(int a, int b, int c){
      String answer = "Error, [int a] must not be equal to zero";
      if(a != 0){
        double xplus = (b*-1 + Math.sqrt((b*b)-(4*a*c)*1.0)) / 2*a ;
        double xminus = (b*-1 - (Math.sqrt((b*b)-(4*a*c)*1.0)) ) / 2*a ;
        answer = "x = " + (int)xplus + "," + "x = " + (int)xminus;
        }
      return answer;
    }
//In this new version, the program returns an error message if a equals 0.