Unit 9 Inheritance

• Notes

Notes

The keyword "Super" is used to call a subclass.

Overriding methods (@Override) is used to give different implementations to the method of the superclass

Subclasses and Superclasses are usually organized into a single root tree caled a hierarchy

One example includes: the Class leaf extends nature, so leaf is a subclass of nature.

public class Team {
    public int score;
    public int wins;
    public int all_goals;

    public Team( int score, int wins, int all_goals) {
        this.score = score;
        this.wins = wins;
        this.all_goals = all_goals;
    }

    public void score() {
        this.score += 1;
    }

    public void bestplayer() {
        System.out.println("Best player: Unknown");
    }

    public void out() {
        System.out.println("Team score: " + this.score);
        System.out.println("Team wins: " + this.wins);
        System.out.println("Team all goals: " + this.all_goals);
        bestplayer();
    }

}

public class Portugal extends Team {
    public Portugal(int score, int wins, int all_goals) {
        super(score, wins, all_goals);
    }

    public void score() {
        this.score += 1;
    }

    public void bestplayer() {
        System.out.println("Best player: Cristiano Ronaldo");
    }
}

public class France extends Team {
    public France(int score, int wins, int all_goals) {
        super(score, wins, all_goals);
    }

    public void score() {
        this.score += 1;
    }

    public void bestplayer() {
        System.out.println("Best player: Kylian Mbappe");
    }
}

Team team = new Team(0, 1, 27);
Team portugal = new Portugal(0, 2, 55);
Team france = new France(0, 2, 129);

team.out();
portugal.out();
france.out();

Team score: 0
Team wins: 1
Team all goals: 27
Best player: Unknown
Team score: 0
Team wins: 2
Team all goals: 55
Best player: Cristiano Ronaldo
Team score: 0
Team wins: 2
Team all goals: 129
Best player: Kylian Mbappe

public class Person {
    protected String name;
    protected String birthday;
 
    public Person (String name, String birthday){
       this.name = name;
       this.birthday = birthday;
    }
 
    public String getName(){
       return name;
    }

    public int getAge() {
         return 2022 - Integer.parseInt(birthday);
    }

    @Override
    public String toString() {
         return "Person (name: " + name + ", birthday: " + birthday + ")";
    }
 }
 
//Student is a subclass and extends person, the superclass, since students are classified as a person.

 public class Student extends Person {
    private int grade;
    private double gpa;
    private String extracurricular;
 
    public Student (String name, String birthday, int grade, double gpa, String extracurricular) {
       super(name, birthday);
       this.grade = grade;
       this.gpa = gpa;
       this.extracurricular = extracurricular;
    }

    // return gpa
    public double getGPA() {
        return gpa;
    }

    public String extracurricular() {
        return extracurricular;
    }

    // return grade
    public int getGrade(){
       return grade;
    }

    @Override
    public String toString() {
         return "Student (name: " + name + ", birthday: " + birthday + ", extracurricular: " + extracurricular + ", gpa:" + gpa + ", grade: " + grade + ")";
    }
 }

// The public class teacher is a subclass of person and as such will extend person, the superclass.

 public class Teacher extends Person {
      private String subject;
      private int tenureYears;
      private String degree;
   
      public Teacher (String name, String birthday, String subject, int tenureYears, String degree) {
         super(name, birthday);
         this.subject = subject;
         this.tenureYears = tenureYears;
         this.degree = degree;
      }
   
      // return subject
      public String getSubject() {
         return subject;
      }
   
      // return yearsOfExperience
      public int getTenure() {
         return tenureYears;
      }
   
      // return degree
      public String getDegree() {
         return degree;
      }

      @Override
      public String toString() {
            return "Teacher (name: " + name + ", birthday: " + birthday + ", subject: " + subject + ", tenureYears:" + tenureYears + ", degree: " + degree + ")";
      }
 }

Person aidan = new Person("aidan", "2006");
System.out.println(aidan.toString());
Person jun = new Student("jun", "2005", 12, 3.5, "football");
System.out.println(jun.toString());
Person allie = new Teacher("allie", "1980", "math", 10, "N/A");
System.out.println(allie.toString());

Person (name: aidan, birthday: 2006)
Student (name: jun, birthday: 2005, extracurricular: football, gpa:3.5, grade: 12)
Teacher (name: allie, birthday: 1980, subject: math, tenureYears:10, degree: N/A)