java核心技术 程序清单5-1 ManagerTest

public class ManagerTest { public static void main(String[] args) { //创建了一个Manager对象，并设置了一个奖金属性 Manager boss = new Manager("Car Cracker", 80000, 1987, 12, 15); boss.setBonus(5000); Employee[] staff = new Employee[3]; //这里是将子类对象的引用赋给父类对象的引用 staff[0] = boss; staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1); staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15); for(Employee e : staff){ //运行第一个e的getSalary()方法时，是调用Manager对象的方法，这里java虚拟机会自动判断，这也是java的特性 **多态** 的表现 System.out.println("name="+e.getName()+",salary="+e.getSalary()); } } } import java.util.Date; import java.util.GregorianCalendar; public class Employee { private String name; private double salary; private Date hireDay; public Employee(String n,double s,int year,int month,int day){ name = n; salary = s; GregorianCalendar calendar = new GregorianCalendar(year,month-1,day); hireDay = calendar.getTime(); } public String getName() { return name; } public double getSalary() { return salary; } public Date getHireDay() { return hireDay; } public void raiseSalary(double byPercent){ double raise = salary * byPercent /100; salary += raise; } } public class Manager extends Employee { private double bonus; //Manager（子类)继承Employee（父类,也叫超类) public Manager(String n,double s,int year,int month,int day){ /* 这里的super(n,s,year,month,day);语句是调用父类Employee中含有n,s,year,month,day参数的构造器的简写。所以super语句必须是子类构造器的第一条语句. 就是说Manager构造器在第一时间必须调用Employee的构造器，接下来才对子类独有的作用域进行初始化。 */ super(n, s, year, month, day); bonus = 0; } public double getSalary(){ //这里就是通过super调用Employee类的getSalary()方法，获得基本工资 double baseSalary = super.getSalary(); return baseSalary + bonus; } public void setBonus(double b){ bonus = b; } }

运行结果 name=Car Cracker,salary=85000.0 name=Harry Hacker,salary=50000.0 name=Tommy Tester,salary=40000.0