ConstructorTest

Posted 2021-03-19 night-watch

 

 1 public class ConstructorTest {
 2 
 3     /**
 4      * 重载构造器
 5      * 用this（...）调用另一个构造器
 6      * 无参数构造器
 7      * 对象初始化块
 8      * 静态初始化块
 9      * 实例域初始化
10      */
11     
12     public static void main(String[] args) {
13         // fill the staff array with three Employee objects
14         Employee[] staff = new Employee[3];
15         
16         staff[0] = new Employee("Harry", 4000);
17         staff[1] = new Employee(60000);
18         staff[2] = new Employee();
19         
20         // print out information about all Employee objects
21         for (Employee e : staff) {
22             System.out.println("name = "+e.getName()+", id = " + e.getId()+", salary = "+e.getSalary());
23             
24         }
25     }
26     
27 }
28 
29 class Employee
30 {
31     private static int nextId;
32     
33     private int id;
34     private String name = "";     // instance field initialization
35     private double salary;
36     
37     static
38     {
39         Random generator = new Random();
40         // set nextId to a random number between 0 and 9999
41         nextId = generator.nextInt(10000);
42     }
43     
44     // object initialization block
45     {
46         id = nextId;
47         nextId++;
48     }
49     
50     // three overloaded constructors
51     public Employee(String n, double s)
52     {
53         name = n;
54         salary = s;
55     }
56     
57     public Employee(double s)
58     {
59         // calls the Employee(String, double) constructor
60         this("Employee #" + nextId, s);
61     }
62     
63     // the default constructor
64     public Employee()
65     {
66         // name initialized to "" --see above
67         // salary not explicitly set --initialized to 0
68         // id initialized in initialization block
69     }
70 
71     public int getId() {
72         return id;
73     }
74 
75     public String getName() {
76         return name;
77     }
78 
79     public double getSalary() {
80         return salary;
81     }
82     
83     
84 }

name = Harry, id = 8654, salary = 4000.0
name = Employee #8655, id = 8655, salary = 60000.0
name = , id = 8656, salary = 0.0