Questions? Email sfo.lax6776@gmail.com

Join our weChat group or follow us on Facebook

©2019 by Legion of Learners

sfolax6776
Apr 12, 2019
Edited: Apr 12, 2019

Test Prep 11 - Dynamic Binding, Interfaces and Abstract Classes

A. Dynamic Binding:

  1. When a super class type of object is declared, the reference(for instance, x) can point to either a _________ class object or a _________class object.

  2. If a method (say, do()) in super class is overridden in the subclass, in the above case, will x.do() call the super class version or sub class version?

  3. Down casting: if a super class reference points to a subclass object, and a "subclass only" method is called, a downcasting is needed to make the call otherwise compile time error will occur.

B. Interfaces:

  1. The story of last digit.

  2. How many interfaces can a class implement? why?

  3. Can interface type be used to declare objects?

C. Abstract Classes:

  1. What if a class implements only part of the interface?

  2. Can abstract classes become super classes?

  3. What if the abstract methods are not implemented in sub classes either?

D. Comparable Interface:


public interface Comparable{
int compareTo(Object obj);
}

E. Challenge of the Week: All MC questions of Chapter 4.

0 comments0 replies
New Posts
  • sfolax6776
    Jan 14

    Test Prep 4: Control Structures, passing arguments and Javadoc

    Discussion 
    A. Review 1) HW check 2) Kahoot! B. H. What are Javadoc Comments? What do @param and @return do? (@throws is useful but won't be tested.) What does short circuit evaluation of logical operators do? I. Which operation has the lowest precedence? J. What is the difference between nested ifs and sequential ifs? What about nested loops and sequential loops? K. How to call static methods and pass arguments?
  • sfolax6776
    Jan 13

    Test Prep 1 - What is AP CS A test?

    Discussion 
    A. Two parts: 50% weight is MC and 50% is FRQ MC: 90 minutes, 40 questions, 1 point each question. No penalty for wrong answers (Yes, take your guess!) FRQ: 90 minutes, 4 coding problems, 9 points each problem. Write code on paper, no penalty for minor syntax errors. B. Strategy for MC: Roughly 2 minutes per question - stay focused when practice Guess is okay - mark guesses for review when time allows An active pencil - hand trace loops, write return values on booklet, use small matrix as examples to test an algorithm Summarize more strategies for each subject when practice C. Strategy for FRQ: 20 min for each question READ carefully, highlight important conditions, restrictions, requirements Write whatever you can, even though it's incomplete The four problems are almost always of the following: Class and objects - how to define classes, create and use of constructors 2-D array - of primitive values, Strings or objects ArrayList of Strings or objects, may use inheritance Interface
  • sfolax6776
    Oct 28, 2019

    11.4 Is it absolutely impossible to insert or remove in arrays?

    Discussion 
    A. Introduction Anything is possible if you can program... :) B. Watch (Slides) C. Try: 1) Do you know ArrayList class is implemented by an array? 2) Can you implement insert/remove for 2-D arrays?