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

public class Employee {

    private String name;

    private double salary;

    private int id = -1;

    private static int nextId = 1;

    {
        System.out.println("开始对象初始化块。。。");
        System.out.println("对象初始化开始前 id:" + id);
        id = 5;
        System.out.println("结束对象初始化块");
        System.out.println("对象初始化结束 id:" + id);
    }

    static {
        System.out.println("开始静态初始化块。。。");
        System.out.println("结束静态初始化块");
    }
    public Employee() {
        System.out.println("无参数的构造方法");
    }

    public Employee(String name, double salary) {
        this();
        this.name = name;
        this.salary = salary;
        this.id = 0;
    }


    public static void main(String[] args) {
        Employee.getNextId();
        Employee e = new Employee("Harry", 50000);
        System.out.println(e.getId() + " " +e.getName() + " " + e.getSalary());
    }
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
        nextId++;
    }

    public static int getNextId() {
        return nextId;
    }

}　　　　　　

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