父类：
package com.demo;
import java.time.LocalDate;
public class Employee {
private String name;
private double salary;
private LocalDate hireDay;
public Employee(String name, double salary, int year,int month, int day){
this.name = name;
this.salary = salary;
this.hireDay = LocalDate.of(year, month,day);
}
public String getName() {
return name;
}
public double getSalary() {
return salary;
}
public LocalDate getHireDay() {
return hireDay;
}
public void raiseSalary(double byPercent){
double raise = salary * byPercent / 100;
salary += raise;
}
}
子类：
package com.demo;
public class Manager extends Employee{
private double bouns;
public Manager(String name, double salary, int year, int month, int day) {
super(name, salary, year, month, day);
bouns = 0;
}
public double getSalary(){
double salary = super.getSalary();
return salary + bouns;
}
public void setBouns(double b){
bouns = b;
}
}
测试类：
package com.demo;
public class ManagerTest {
public static void main(String[] args) {
var boss = new Manager("Carl Craker", 80000,1987,12,15);
boss.setBouns(5000);
var staff = new Employee[3]; // java 10 新特性：如果可以从变量的初始值推到出它们的类型，
// 那么可以使用car关键字声明变量类，无须指定类型
staff[0] = boss;
staff[1] = new Employee("Harry Hacker", 50000,1989,10,1);
staff[2] = new Employee("Tommy Tester", 40000,1990,3,15);
if (staff[0] instanceof Manager){
Manager boss2 = (Manager) staff[0];
System.out.println(boss2.getSalary());
}
}
}
对于以下类型写法有些冗余，Manager 被提及了三次
if (staff[0] instanceof Manager){
Manager boss2 = (Manager) staff[0];
System.out.println(boss2.getSalary());
}
在Java16中，还有一种更简便的写法。可以直接在instanceof 测试中声明子类变量:
if (staff[0] instanceof Manager boss2){
System.out.println(boss2.getSalary());
}
//还可以有其他类似的用法
if (staff[0] instanceof Manager m && m.getSalary() >10000){
System.out.println(m.getSalary());
}
//比如 三元运算符的用法
double bouns = staff[0] instanceof Manager m ? m.getSalary() : 0;