Superclass Removed

A class removes its superclass.

Example

The class LandVehicles in the library project removes the superclass Vehicle from its declaration.

public abstract class Vehicle {
  public static final int INITIAL_KMS = 0;

  String getType();

  public static void move() {
    System.out.println("The vehicle is moving.");
  }

}

-public abstract class LandVehicles extends Vehicle {
+public abstract class LandVehicles {

}

Broken Uses

Hereafter, we list the broken uses that are currently detected by Maracas.

• 1. Methods overriding methods declared in the now-removed superclass
• 2. Accesses of fields declared in the now-removed superclass
• 3. Invocations of static or default methods declared in the now-removed superclass
• 4. Casts of subtypes referencing the now-removed superclass

1. Methods overriding methods declared in the now-removed superclass

Example

The concrete Car class in a client project extends the LandVehicle abstract class defined in the library. The Car overrides the getType() method declared within the now-removed superclass (i.e. Vehicle). Then, a broken use is reported pointing to the client method declaration.

public class Car extends LandVehicle {
  private String type;

  // Broken use reported here
  @Override
  public String getType() {
    return this.type;
  }

}

2. Accesses of fields declared in the now-removed superclass

Example

The concrete Car class in a client project extends the LandVehicle abstract class defined in the library. The resetKms() method is defined within the Car class and it accesses the INITIAL_KMS constant defined in the Vehicle class. Then, a broken use is reported pointing to the line of the field access expression.

public class Car extends LandVehicle {
  public void resetKms() {
    // Broken use reported here
    this.kms = LandVehicle.INITIAL_KMS;
  }

}

3. Invocations of static or default methods declared in the now-removed superclass

Example

The concrete Car class in a client project extends the LandVehicle abstract class defined in the library. The moveCar() method is defined within the Car class and it invokes the move() method defined in the Vehicle class. Then, a broken use is reported pointing to the line of the method invocation expression.

public class Car extends LandVehicle {
  public void moveCar() {
    // Broken use reported here
    move();
    System.out.println("It is a car!");
  }

}

4. Casts of subtypes referencing the now-removed superclass

Example

On the one hand, the concrete Car class in a client project extends the LandVehicle abstract class defined in the library. On the other hand, the VehicleFactory class within the same client project defines the createCar() method. Such method creates a Car instance and casts it to a Vehicle object. Then, a broken use is reported pointing to the cast expression.

public class Car extends LandVehicle { }

public class VehicleFactory {
  public Vehicle createCar() {
    // Broken use reported here
    Vehicle vehicle = (Vehicle) new Car();
    return vehicle;
  }

}