Visibility

Recall how access modifiers determine which fields and methods a class can use.

Modifier	Class Access
public	Any class
protected	Same package and subclasses
(default)	Same package
private	Same class only

protected fields are available to any subclasses.

For example, Boat, Automobile, and Truck can access Vehicle's purchasePrice because the field is protected.

public class Vehicle {

  protected double purchasePrice;
  // ...
}

public class Boat extends Vehicle {
  protected String name;
  protected double speedInKnots;
  protected int lengthInFeet;

  public Boat(double purchasePrice, String name, double speedInKnots, int lengthInFeet) {
    this.purchasePrice = purchasePrice;  // Field inherited from Vehicle

    this.name = name;
    this.speedInKnots = speedInKnots;
    this.lengthInFeet = lengthInFeet;
  }

  public String toString() {
    return "Boat [purchasePrice=" + purchasePrice   // Field inherited from Vehicle
    + ", name=" + name
    + ", speedInKnots=" + speedInKnots
    + ", lengthInFeet=" + lengthInFeet + "]";
  }
  // ...
}

Inheritance and Encapsulation

protected allows subclasses to access fields, but also allows any class in the package to access these fields. * This is poor encapsulation. * The strongest level of encapsulation is to make fields private.

If we make fields private, subclasses can no longer access them.

private Members Are Not Inherited

private members (fields and methods) are not inherited from a superclass. * These fields and methods are not directly accessible to the subclass, so they cannot be considered inherited.

A subclass cannot see a private field or call a private method.

Drill

Inheritance/com.example.inheritance.drills * Create a class DataAnalyst which extends Employee. * Add a field private String securityClearance, with a getter and setter. * Add a one-arg constructor to set the private field. * Add a method public String getInfo() * Return a String containing the firstName, lastName, age, title, salary, and securityClearance. * Remember that firstName and lastName are accessible with getName() in Person. Use this method. * You should see errors for the private fields title and salary, inherited from Employee. * Remove title and salary from your method. We will add them in later.

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