java 类

1. 构造器的重载

2. 默认构造器

3. 对象初始化块

4. 静态初始化块

5. 实例域初始化

 1 public class Employee {
 2 
 3     private String name;
 4 
 5     private double salary;
 6 
 7     private int id = -1;
 8 
 9     private static int nextId = 1;
10 
11     {
12         System.out.println("开始对象初始化块。。。");
13         System.out.println("对象初始化开始前 id:" + id);
14         id = 5;
15         System.out.println("结束对象初始化块");
16         System.out.println("对象初始化结束 id:" + id);
17     }
18 
19     static {
20         System.out.println("开始静态初始化块。。。");
21         System.out.println("结束静态初始化块");
22     }
23     public Employee() {
24         System.out.println("无参数的构造方法");
25     }
26 
27     public Employee(String name, double salary) {
28         this();
29         this.name = name;
30         this.salary = salary;
31         this.id = 0;
32     }
33 
34 
35     public static void main(String[] args) {
36         Employee.getNextId();
37         Employee e = new Employee("Harry", 50000);
38         System.out.println(e.getId() + " " +e.getName() + " " + e.getSalary());
39     }
40     public String getName() {
41         return name;
42     }
43 
44     public void setName(String name) {
45         this.name = name;
46     }
47 
48     public double getSalary() {
49         return salary;
50     }
51 
52     public void setSalary(double salary) {
53         this.salary = salary;
54     }
55 
56     public int getId() {
57         return id;
58     }
59 
60     public void setId(int id) {
61         this.id = id;
62         nextId++;
63     }
64 
65     public static int getNextId() {
66         return nextId;
67     }
68 
69 }　　　　　　

执行结果：

开始静态初始化块。。。
结束静态初始化块
开始对象初始化块。。。
对象初始化开始前 id:-1
结束对象初始化块
对象初始化结束 id:5
no paramter con
0 Harry 50000.0