物件導向設計:99年期末考古

[學院]：資電學院
[系所]：資訊工程學系
[年級]：二
[學程]：SE軟體工程
[課名]：物件導向設計
[老師]：張貴忠老師
[學期]：99-1
[類型]：期末考

Totally 100 points
1. ( Inner Class – 5 pts) What are two advantages to use inner classes?
ANSWER：There are two big advantages to using inner classes. First, because they are defined within a class, they can be used to make the outer class self-contained. The second advantage is that the inner and outer classes’ methods have access to each other’s private methods and private instance variables.



2. (The final Modifier – 15 pts) What are the meanings of final class, final variable, and
final method？
ANS: Final class：不可被繼承的class
Final variable：一經給定就不可變動的常數
Final method：不可被overrided的method



3. (Inheritance - 10 pts) What are the differences between overloading and overriding？
ANS：overloading：在同一class中，相同名稱的method，使用不同的回傳型態或不同的傳入參數來作區別
overriding：繼承之後，如果覺得父類別的method不符使用，可在子類別中定義一模一樣的method來修改
不同處：繼承與非繼承 / 宣告部份一樣與宣告一模一樣



4. (Event-Driven Programming – 15 pts) Please explain what is event-driven
programming ？ What are the differences between traditional programming and
event-driven programming?
ANS：event-driven programming：在程式執行的時候，是依靠某些事件(如：鍵盤滑鼠)來決定程式之後的執行，跟傳統的程式不同在於控制流程的改變



5. (Inheritance & Polymorphism - 20 pts) Find all compiler-time errors in the following codes and give brief explanations about these errors. When you correct all errors, please write down the output of this program.

public class A
{
String msg;
public A(String msg)
{
this.msg = msg;
}
public void sayHello()
{
System.out.println(“A:” + msg);
}
public void say()
{
sayHello();
}
}
public class B extends A
{
String value;
public B()
{
value = 0;
super("I'm class B");
}
public B(String msg)
{
super(msg);
value = 0;
}
public B(int val)
{
value = val;
}
private void sayHello()
{
System.out.println(“B:” + msg);
}
}
public class C
{
public static void main(String[] args)
{
A obj1 = new A(“I’m Class A”);
B obj2 = new B();
C mainObj = new C();
mainObj.showMessage(obj1);
mainObj.showMessage(obj2);
}
public void showMessage(A member)
{
member.say();
}
}


6. (Exception Handling - 10 pts) What’s the problem about the following code segment?
(類似概念的程式碼)

try
{
throw new Exception(StringArqument);
}

catch (Exception e)
{
System.out.println(e.getMessage());
}

catch (ArithmeticException e)
{
System.out.println("In ArithmeticException"+e.getMessage());
}


7. (Array – 10 pts) What’s the problem about the following code segment?
(類似概念的程式碼)

public class objArray
{
        private int i;
        private String s;
        public void method1()
        {
            i=0;
        }
        public void method2(String theString)
        {
            s=theString;
        }
}
public static void main(String[] args)
{
        objArray[] oa = new objArray[10];
        oa[0].method1();
        oa[10].method2("hahaha");
}

8. (Access Modifiers - 15 pts) Given the following codes, and some compile-time errors exist in this program. Please precisely indicate the line numbers of error statements in the program. (Remember to briefly explain why the indicated statement is error.)
1 package mypackage;
2 public class A {
3 public int v1;
4 protected int v2;
5 int v3;
6 private int v4;
7 }
8 package mypackage;
9 public class B {
10 public B() {
11 A obj1 = new A();
12 obj1.v1 = 10;
13 obj1.v2 = 10;
14 obj1.v3 = 10;
15 obj1.v4 = 10;
16 }
17 }
18 package mypackage;
19 public class C extends A {
20 public C() {
21 v1 = 10;
22 v2 = 10;
23 v3 = 10;
24 v4 = 10;
25 }
26 }
27 import mypackage.A;
28 public class D extends A {
29 public D() {
30 v1 = 10;
31 v2 = 10;
32 v3 = 10;
33 v4 = 10;
34 }
35 }
36 public class E {
37 public E() {
38 A obj1 = new A();
39 obj1.v1 = 10;
40 obj1.v2 = 10;
41 obj1.v3 = 10;
42 obj1.v4 = 10;
43 }
44 }