K. Rajkumar: JAVA Programming, 1/e

Listing 5.3. Object-Oriented College

1. Listing 5.3. Object-Oriented College
   
2. 
   
3. // OOCollege.java
   
4. 
   
5. class Course
   
6. {
   
7.   String cid; // course id
   
8. }
   
9. 
   
10. class Department
    
11. {
    
12.   String did; // department id
    
13. }
    
14. 
    
15. class Student
    
16. {
    
17.   String sid; // student id
    
18. }
    
19. 
    
20. class Professor
    
21. {
    
22.   String pid; // professor id
    
23. }
    
24. 
    
25. public class OOCollege
    
26. {
    
27.   Course c = new Course(); // here, only one course available
    
28.   Department d = new Department(); // only one department
    
29.   Student s = new Student(); // only one student
    
30.   Professor p = new Professor(); // only one professor
    
31.   // but array of objects can be created
    
32. 
    
33.   public void startCollege()
    
34.   {
    
35.     c. cid = “CS001”; // use dot operator to access variables
    
36.     d. did = “CS”;
    
37.     s.sid = “UCS001”;
    
38.     p.pid = “FCS001”;
    
39. 
    
40.     System.out.println(“College Started”);
    
41.   }
    
42. 
    
43.   public static void main(String[] args)
    
44.   {
    
45.     OOCollege c = new OOCollege();
    
46.     c.startCollege();
    
47.   }
    
48. }

复制代码

Listing 5.4. DataMembersTest Application

1. Listing 5.4. DataMembersTest Application
   
2. 
   
3. 
   
4. 
   
5. // DataMembersTest. java
   
6. 
   
7. class DataMembers
   
8. {
   
9.   public int i = 100;
   
10.   private float f = 200f;
    
11.   double d = 300;
    
12.   public static int si = 10;
    
13.   public final int MAX = 1000;
    
14. }
    
15. 
    
16. public class DataMembersTest
    
17. {
    
18.   public static void main(String[] args)
    
19.   {
    
20.     // create object
    
21.     DataMembers d1 = new DataMembers();
    
22.     DataMembers d2 = new DataMembers();
    
23. 
    
24.     // access data members, instance variables by dot operator
    
25. 
    
26.     System.out.println(“d1.i ” + d1.i); // 100
    
27.     System.out.println(“d2.i ” + d2.i); // 100
    
28. 
    
29.     // error: f has private access in DataMembers
    
30.     // System.out.println(“d1.f ” + d1.f); // error
    
31.     // System.out.println(“d1.f ” + d1.f); // error
    
32. 
    
33.     System.out.println(“d1.d ” + d1.d); // 300.0
    
34.     System.out.println(“d1.d ” + d1.d); // 300.0
    
35. 
    
36.     System.out.println(“d1.si ” + d1.si); // 10
    
37.     System.out.println(“d2.si ” + d2.si); // 10
    
38.     System.out.println(“DataMembers.si ” + DataMembers.si); // 10
    
39. 
    
40.     // increment si using class name
    
41.     DataMembers.si++;
    
42.     System.out.println(“d1.si ” + d1.si); // 11
    
43.     System.out.println(“d2.si ” + d2.si); // 11
    
44.     System.out.println(“DataMembers.si ” + DataMembers.si); // 11
    
45. 
    
46.     // increment si using instance variable d1
    
47.     d1.si++;
    
48.     System.out.println(“d1.si ” + d1.si); // 12
    
49.     System.out.println(“d2.si ” + d2.si); // 12
    
50.     System.out.println(“DataMembers.si ” + DataMembers.si); // 12
    
51. 
    
52.     System.out.println(“d1.max ” + d1.MAX); // 1000
    
53.     System.out.println(“d2.max ” + d2.MAX); // 1000
    
54.     // error: cannot assign value to final variable max
    
55.     //d1.MAX++; // error
    
56.     //d2.MAX++; // error
    
57.   }
    
58. }

复制代码