add gradebook class

Author: CarlyLanglois

src/org/launchcode/java/demos/collections/Gradebook.java

@@ -0,0 +1,46 @@
+package org.launchcode.java.demos.collections;
+
+import java.util.ArrayList;
+import java.util.Scanner;
+
+public class Gradebook {
+
+    public static void main(String[] args) {
+
+        ArrayList<String> students = new ArrayList<>();
+        ArrayList<Double> grades = new ArrayList<>();
+        Scanner in = new Scanner(System.in);
+        String newStudent;
+
+        System.out.println("Enter your students (or ENTER to finish):");
+
+        // Get student names
+        do {
+            newStudent = in.nextLine();
+
+            if (!newStudent.equals("")) {
+                students.add(newStudent);
+            }
+
+        } while(!newStudent.equals(""));
+
+        // Get student grades
+        for (String student : students) {
+            System.out.print("Grade for " + student + ": ");
+            Double grade = in.nextDouble();
+            grades.add(grade);
+        }
+
+        // Print class roster
+        System.out.println("\nClass roster:");
+        double sum = 0.0;
+
+        for (int i = 0; i < students.size(); i++) {
+            System.out.println(students.get(i) + " (" + grades.get(i) + ")");
+            sum += grades.get(i);
+        }
+
+        double avg = sum / students.size();
+        System.out.println("Average grade: " + avg);
+    }
+}