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Home KS3 GCSE A-Level Programming

Lesson 8. Inheritance

Lesson Notes

Inheritance

In Java, it is possible to inherit attributes and methods from one class to another. The "inheritance concept" is categorized into two groups:

• subclass (child) - the class that inherits from another class.
• superclass (parent) - the class being inherited from.

In Java, to inherit from a class, use the extends keyword.

In the following example, the P16_Student class (subclass) inherits the attributes and methods from the Student class (superclass)

public class Main {
    public static void main(String[] args) {
       P16_Student stu24 = new P16_Student();
       stu24.setName("Fei");
       stu24.setAge(17);
       System.out.print(stu24.getName());
       System.out.print(" is ");
       System.out.println(stu24.getAge());
    }
}
// New class inherits from Student superclass.

public class Student {
    private String name;
    private int age;
    // Note: Constructor has been removed in this example.
    public String getName() {
        return name;
    }
    public void setName(String n) {
        name = n;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int a) {
        age = a;
    }
}

public class P16_Student extends Student{

}

Fei is 17

super is used to refer to the superclass, which will send data to the constructor in the superclass to the subclass.

public class Main {
  public static void main(String[] args) {
      P16_Student stu24 = new P16_Student("Fei",17,false);
      System.out.println(stu24.getName()+" is "+stu24.getAge());
      System.out.println("UCAS complete: "+stu24.getUCAS());
    }
}
// Method specific to the P16_Student Class used here.

public class Student {
    private String name;
    private int age;
    public Student (String n, int a){
        name = n;
        age = a;
    }
    public String getName() {
        return name;
    }
    public void setName(String n) {
        name = n;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int a) {
        age = a;
    }
}
// Original Student Constructor has been placed back into the Student Class.

public class P16_Student extends Student{
    private boolean UCAS;

  public P16_Student(String n,int a,boolean u){
       super (n,a);
       UCAS = u;
   }
   public boolean getUCAS() {
       return UCAS;
   }
   public void setUCAS(boolean u) {
       UCAS = u;
   }
}
// New P16_Student Constructor has been created in this class. super is used to specify which parameters are inherited from the student superclass.

Fei is 17
UCAS complete: false