A1: Specifying and Using Abstraction
CPSC 210
Learning Goals
- Specify the methods in a data abstraction using appropriate REQUIRES, MODIFIES & EFFECTS clauses
-
Once the methods of a data abstraction have been specified, demonstrate how those methods could be used
- i.e. write examples of calls to those methods
Abstraction Concepts
Visibility
Objects of a different class (type) can access/use it
Only objects of the same class (type) can use/access it
Private
Public
public class Dog {
private String name;
public Dog(String name) { this.name = name; }
private void makeOtherDogBark(Dog otherDog) {
otherDog.bark();
}
public void bark() {
System.out.println("BAARRRRK");
}
public void barkAndMakeOtherDogBark(Dog otherDog) {
this.bark();
this.makeOtherDogBark(otherDog);
}
}
public class Main {
public static void main(String[] args) {
Dog peter = new Dog("Peter");
Dog paul = new Dog("Paul");
peter.bark();
peter.barkAndMakeOtherDogBark(paul);
peter.makeOtherDogBark(paul);
}
}Visibility
Parts of a Method
private void makeOtherDogBark(Dog otherDog) {
System.out.println("Woof Woof Woof Woof Woof"):
}Visibility
Return Type
Method Name
Parameter List
Method body
}
the body goes between { ... }
Specification
// Requires// Modifies// Effects- Conditions that must be true when the call to the method is made
States if the object itself changes (this)
States if some other object changes (name the object)
No internal implementation details
- Externally visible effects
- No internal details or variable names
- No description for how you accomplish these effects
- No description of algorithm in detail
Lecture Ticket Review
public class Person {
private int age;
private String status;
private String name;
public Person() {
this.status = "young";
this.age = 0;
this.name = "Unnamed Person";
}
public int getAge() { return age; }
public String getName() { return name; }
public void setName(String name) {
this.name = name;
}
public void getOlderByYears(int years) {
this.age = this.age + years;
if (age > 10) { this.status = "old"; }
}
}
🏗️ Lecture Lab
A1: Specifying and Using Abstraction
The End - Thank You!
CPSC210 - A1 Specifying and Using Abstraction
By meghanallen
