Answers to Questions and Exercises: Managing Inheritance - Java Tutorial 5.0 英文版

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Answers to Questions and Exercises: Managing Inheritance

Questions

Question 1: Consider the following two classes:

public class ClassA {
    public void methodOne(int i) {
    }
    public void methodTwo(int i) {
    }
    public static void methodThree(int i) {
    }
    public static void methodFour(int i) {
    }
}

public class ClassB extends ClassA {
    public static void methodOne(int i) {
    }
    public void methodTwo(int i) {
    }
    public void methodThree(int i) {
    }
    public static void methodFour(int i) {
    }
}

Question 1a: Which method overrides a method in the superclass?
Answer 1a: methodTwo

Question 1b: Which method hides a method in the superclass?
Answer 1b: methodFour

Question 1c: What do the other methods do?
Answer 1c: They cause compile-time errors.

Question 2: Consider the Card, Deck, and DisplayDeck classes you wrote in the previous exercise. What Object methods should each of these classes override?
Answer 2: Card should override equals, hashCode, and toString.

Exercises

Exercise 1: Write the implementations for the methods that you answered in question 2.
Answer 1: See Card2.

Exercise 2: Write an abstract class. Write at least two of its nonabstract subclasses.
Answer 2: If you tell us your solution, we'll post the best one.

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