setParentAttribute(value1) OR super(value1, ...)

Week 5: Class hierarchies/03A. Adding features to child class

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+The idea of inheritance is usually to ADD NEW FEATURES to SUBCLASSES, 
+i.e. to SPECIALISE the activities of classes. 
+Let's continue developing the 'Student' class by writing a constructor for it, 
+which will have a name and an email address as well as a number of credits as parameters. 
+
+
+In addition, write setting and observation methods for the number of credits:
+class Student extends Person {
+    // new attribute,  that person does not have
+    private int studypoints;
+
+    //CONSTRUCTOR
+    public Student(String name, String email, int studypoints) {
+        // Setting attributes from parents class
+        // by CALLING METHODS INHERITED from it
+        setName(name);
+        setEmail(email);
+        
+        // child class's "own" attribute
+        this.studypoints = studypoints;
+    }
+
+    public int getStudypoints() {
+        return studypoints;
+    }
+
+    public void setStudypoints(int studypoints) {
+        this.studypoints = studypoints;
+    } 
+}
+ 
+
+Now we can form an object from the Student class:
+Student sam = new Student("Sam Student", "sam@example.com", 123);
+System.out.println(sam.getStudypoints()); 
+ 
+
+Program outputs:
+123
+ 
+
+
+
+
+Since 'Student' inherits the class 'Person', the features of the 'Person' class are also available. 
+The 'Student' class instance can therefore also be used to call the 
+name and email configuration and observation methods, for example:
+
+Student sam = new Student("Sam Student", "sam@example.com", 123);
+System.out.println(sam.getStudypoints());
+System.out.println(sam.getName());
+System.out.println(sam.getEmail());
+ 
+
+Program outputs:
+123
+Sam Student
+sam@example.com
+ 
+
+
+
+
+
+Let's also implement the constructor and new setting and observation methods in the Teacher class:
+class Teacher extends Person {
+    private int courses;
+
+    public Teacher(String name, String email, int courses) {
+        setName(name);
+        setEmail(email);
+        this.courses = courses;
+    }
+
+    public int getCourses() {
+        return courses;
+    }
+
+    public void setCourses(int courses) {
+        this.courses = courses;
+    }
+}
+ 
+
+Now the teacher and the pupil have not only common characteristics, but also their own:
+
+Student sam = new Student("Sam Student", "sam@example.com", 123); 
+Teacher tina = new Teacher("Tina Teacher", "tina@example.com", 4);
+
+// both have a name and an email
+System.out.println(sam.getName());
+System.out.println(sam.getEmail());
+
+System.out.println(tina.getName());
+System.out.println(tina.getEmail());
+
+// only student has study points
+System.out.println(sam.getStudypoints());
+ 
+// only teacher has course amount
+System.out.println(tina.getCourses());
+ 
+
+Program outputs:
+Sam Student
+sam@example.com
+Tina Teacher
+tina@example.com
+123
+4
+
+
+=================================
+
+
+
+
+Calling 'parent class constructor'
+In the previous examples, the values inherited from the parent class were set using the setting methods. 
+However, it would be easier to 'CALL the PARENT CLASS CONSTRUCTOR DIRECTLY, especially if there are MANY VALUES TO SET'.
+
+This can be done with the 'super' keyword. It can be used to refer from a child class to a parent class.
+
+Let's start by writing a constructor for the 'Person' class to set the values of the attributes:
+// PARENT CLASS
+class Person {
+    private String name;
+    private String email;
+    
+    public Person (String name, String email) {
+        this.name = name;
+        this.email = email; 
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }  
+}
+ 
+
+
+
+
+Then modify the Student class so that its constructor calls the parent class constructor:
+class Student extends Person {
+    // new attribute that the person does not have
+    private int studypoints;
+    
+    public Student(String name, String email, int studypoints) {
+        super(name, email);
+        this.studypoints = studypoints;
+    }
+
+    public int getStudypoints() {
+        return studypoints;
+    }
+
+    public void setStudypoints(int studypoints) {
+        this.studypoints = studypoints;
+    } 
+}
+ 
+
+
+
+
+
+Let's make a similar change to the Teacher category:
+class Teacher extends Person {
+    private int courses;
+
+    public Teacher(String name, String email, int courses) {
+        super(name, email);
+        this.courses = courses;
+    }
+
+    public int getCourses() {
+        return courses;
+    }
+
+    public void setCourses(int courses) {
+        this.courses = courses;
+    }
+}
+
+