【Java补充】对象构造

import java.util.Random;

public class Dome2 {
    public  static  void  main(String[] args) {
        Employee[] staff = new Employee[3];

        staff[0] = new Employee("Ha", 4000);
        staff[1] = new Employee(8000);
        staff[2] = new Employee();

        for (Employee e : staff) {
            System.out.println("name=" + e.getName() + " id=" + e.getId() + " salary=" + e.getSalary());
        }
    }

}

class Employee{
    private  static  int nextId;

    private int id;
    private String name = "";
    private double salary;

    static {
        Random generator = new Random();
        nextId = generator.nextInt(10000);
    }

    {
        id=nextId;
        nextId++;
    }

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

    public Employee(double salary) {
        this("Employee #" + nextId, salary);
    }

    public Employee(){

    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }
}

运行结果

name=Ha id=622 salary=4000.0
name=Employee #623 id=623 salary=8000.0
name= id=624 salary=0.0

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案例中使用的特性

• 重载构造器
• 用 this(...) 调用另一个构造器
• 无参数构造器
• 对象初始化块
• 静态初始化块
• 实例域初始化

Java初始化顺序