this.attr1 = new ArrayList<Class1>();

Week 5: Class hierarchies/06. Class gradebook

@@ -0,0 +1,87 @@
+Write a category 'Gradebook' with the following properties
+Attribute owner of type string
+Attribute grades, whose type is a list. The list must be able to store objects of type Grade (the class can be found in the attached program)
+A constructor that takes the owner as a parameter and sets the value of the attribute. The constructor also initializes the grade list.
+The attributes must be 'protected' so that the client cannot see them, but any inheriting classes can.
+
+
+import java.util.Random;
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+
+public class Test{
+    public static void main(String[] args){
+        final Random r = new Random();
+        
+        
+        System.out.println("Testing class Gradebook...");
+        Gradebook gb = new Gradebook("Gary Grader");
+        
+        System.out.println("Object created!");
+        
+        try {
+            Field number = gb.getClass().getDeclaredField("owner");
+            boolean numberPrivate = number.getModifiers() == 4;
+            System.out.println("Owner is protected: " + numberPrivate);
+        } catch (Exception e) {
+            System.out.println("Attribute owner is not defined");
+        }
+        
+        try {
+            Field grades = gb.getClass().getDeclaredField("grades");
+            boolean asPrivate = grades.getModifiers() == 4;
+            System.out.println("Grades is protected: " + asPrivate);
+            
+            ArrayList<Grade> as = gb.grades;
+            boolean isInitialized = gb != null;
+            System.out.println("Grades is initialized: " + isInitialized);
+        } catch (Exception e) {
+            System.out.println("Attribute grades is not initialized");
+        }
+    }
+}
+
+class Grade {
+    private String student;
+    private int grade;
+    
+    public Grade(String student, int grade) {
+        this.student = student;
+        this.grade = grade;
+    }
+
+    public String getStudent() {
+        return student;
+    }
+
+    public int getGrade() {
+        return grade;
+    }
+
+}
+
+
+
+
+
+
+//add
+class Gradebook {
+    protected String owner;
+    protected ArrayList<Grade> grades;
+
+    // constructor
+    public Gradebook(String owner) {
+        this.owner = owner;
+        this.grades = new ArrayList<Grade>();
+    }
+}
+
+
+
+Testing class Gradebook...
+Object created!
+Owner is protected: true
+Grades is protected: true
+Grades is initialized: true
+