(1) 此程式中有一列 super(999);
第一個做出含該列以及不含該列之 running script
並且正確說明有何不同的可以賺到期中考3分
(2) 此程式改自以前給大家的man.C 之C++程式(Animal, Mankind 繼承範例)
試著與之對照看看, (man.C 在/net/ftp/pub/CSIE/course/cs2/man.C )
第一個正確列出C++和Java在這範例看出哪些不同規定的可以賺到期中考3分
follow up 時注意你的引言形式
1 //to test constructor / inheritance, CopyLeft by tsaiwn@csie.nctu.edu.tw
2 // this testM.java will generate three .class files; 也可拆成三個.java程式檔
3 class Animal {
4 int pv1; //注意沒寫屬性並非"private", 是package available,此與C++不同
5 private double pv2;
6 protected int pt1[]={0,1,2,3,4};
7 public float pb1;
8 public int pb2[]={10, 11,12,13,14,15,16};
9 public Animal(){ System.out.println("Animal pop out!");};
10 public Animal(String x){ System.out.println("Animal String "+x);};
11 public Animal(int x){
12 pv1=x; pv2=45.67;
13 this.pb1=135.246f;
14 System.out.println("Animal shows up");
15 };
16 void talk() {
17 System.out.println("Animal talk, pv1="+pv1);
18 System.out.println("\t pv2="+ pv2);
19 System.out.println("\t pb1="+ pb1);
20 System.out.println("\t pb2[6]="+ pb2[6]);
21 };
22 };
23 class Mankind extends Animal{
24 String pv3;
25 public Mankind(String name) { // Constructor
26 super(999); // TRY to COMMENT OUT this line and Test again
27 pv3=name; // .. 注意若沒寫super(999); 等於寫 super();
28 System.out.println("Mankind "+ pv3 + " appears");
29 }
30 public int pb3[]={30,31,32,33,34,35,36,37,38};
31 public void talk() {
32 System.out.print("Mankind talk, pb2[0]=" + pb2[0]);
33 System.out.println(", pv3=" + pv3 );
34 System.out.println("Mankind talk, pt1[3]=" + pt1[3]);
35 System.out.println("Mankind talk, pb3[3]=" + pb3[3]);
36 System.out.println(" pv1="+pv1);
37 // System.out.println(" pv2="+pv2); //error, 因private
38 };
39 } // C++ 需要用 ";" 結束class, 但 Java 不必了
40 public class testM{ // filename 必須與此public class 同名: testM.java
41 static Animal a, aa1=new Animal(123), aa2= new Animal(456);
42 static Mankind mm1, mm2; // object reference only, no object yet
43 public static void main(String s[]){ //別忘了static且參數是String array
44 System.out.println("Welcome to taste Java ---first let aa1 talk:");
45 aa1.talk();
46 mm1= new Mankind("Chang-3");
47 mm2= new Mankind("Lee-4");
48 System.out.println("mm1.pb1=" + mm1.pb1);
49 System.out.print(" (Let mm1 talk)\n"); mm1.talk();
50 System.out.print(" (and then DO a=mm2; a.talk();)\n");
51 a = mm2; // 這是可以的, 因為 a 屬於 mm2 所屬的父類別(super class)
52 a.talk(); // 仍會用 Mankind 裡的 talk(); 因Polymorphism 多型!
53 System.out.print(" (and then DO mm2=(Mankind)aa1; mm2.talk();)\n");
54 mm2 = (Mankind) aa1; // "cast" is required! 但仍會Runtime Exception
55 //mm2.talk();
56 }
57 } //(別告訴我說你到現在還不會將此篇存檔然後去掉line numbers)
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