How can I get my input validation to work so anything outside range -1 - 100 will display the error message?

public static void main(String[] args) {
// Defining the constants for min and max range
final int minValue = -1;
final int maxValue = 100;
String message = "Welcome to Simple Gradebook!";
promptForInt(message, minValue, maxValue);
// Declaring variables for the loop & the sentinel variable
int score = 0;
boolean doneYet = false;
do {
// Input Validation
if (score < minValue || score > maxValue) {
System.err.printf(
"Invalid value. The acceptable range is" + " between %d and %d\n" + "Please try again\n",
minValue, maxValue);
score = promptForInt(message, minValue, maxValue);
} else {
doneYet = true;
}
} while (doneYet == false);
}
public static int promptForInt(String message, int minValue, int maxValue) {
// Declaring variables for the loop & the sentinel variable
int sum = 0;
int numStudents = 0;
int score = 0;
System.out.println(message);
// Creating the sentinel loop
do {
System.out.printf("Enter the score for student #%d" + "(or -1 to quit): ", numStudents);
Scanner keyboard = new Scanner(System.in);
score = Integer.parseInt(keyboard.nextLine());
if (score != -1) {
sum += score;
numStudents += 1;
}
} while (score != -1);
double avgScore = (double) sum / numStudents;
// Passing method to this method to convert grade to letter
convertToLetter(avgScore);
System.out.println("The average score is: " + avgScore + " which equates to a " + avgScore);
return 0;
}

How can I get my input validation to work so anything outside range -1 - 100 will display the error message? I want to use the "do-while" loop and thought I was doing it all correctly. If a user enters a value outside the defined range, it should display the error message and prompt again for the score. What am I missing?

1. A good place to do the validation is inside the method, promptForInt.
2. Since there is no use of the value returned from method, promptForInt, it's better to declare it as void.
3. Do not instantiate the Scanner object inside the loop.

The following code has incorporated all these comments:

import java.util.Scanner;
public class Main {
public static void main(String[] args) {
// Defining the constants for min and max range
final int minValue = -1;
final int maxValue = 100;
String message = "Welcome to Simple Gradebook!";
promptForInt(message, minValue, maxValue);
}
public static void promptForInt(String message, int minValue, int maxValue) {
// Declaring variables for the loop & the sentinel variable
int sum = 0;
int numStudents = 0;
int score = 0;
boolean valid;
Scanner keyboard = new Scanner(System.in);
System.out.println(message);
// Loop to continue getting score for students until -1 is entered to quit
do {
System.out.printf("Enter the score for student #%d" + "(or -1 to quit): ", numStudents);
// Loop for getting input of score for the current student
do {
valid = true;
score = Integer.parseInt(keyboard.nextLine());
// Input Validation
if (score < minValue || score > maxValue) {
System.err.printf(
"Invalid value. The acceptable range is" + " between %d and %d\n" + "Please try again\n",
minValue, maxValue);
valid = false;
}
} while (!valid);
if (score != -1) {
sum += score;
numStudents += 1;
}
} while (score != -1);
double avgScore = (double) sum / numStudents;
// Passing method to this method to convert grade to letter
convertToLetter(avgScore);
System.out.println("The average score is: " + avgScore + " which equates to a " + convertToLetter(avgScore));
}
public static char convertToLetter(double avg) {
char gradeLetter;
// Identifying the ranges for the grade letter
if (avg >= 90) {
gradeLetter = 'A';
} else if (avg >= 80) {
gradeLetter = 'B';
} else if (avg >= 70) {
gradeLetter = 'C';
} else if (avg >= 60) {
gradeLetter = 'D';
} else {
gradeLetter = 'F';
}
return gradeLetter;
}
}

A sample run:

Welcome to Simple Gradebook!
Enter the score for student #0(or -1 to quit): -2
Invalid value. The acceptable range is between -1 and 100
Please try again
-4
Invalid value. The acceptable range is between -1 and 100
Please try again
45
Enter the score for student #1(or -1 to quit): 50
Enter the score for student #2(or -1 to quit): -1
The average score is: 47.5 which equates to a F