多态04 多态的应用（多态数组）

一、多态数组

数组的定义类型为父类类型，里面保存的实际元素类型为子类类型。

1、应用实例

应用实例：现有一个继承结构如下：Student类 和 Teacher类继承Person类（属性private，name-String; age-int; say()-String）

要求创建1个Person对象、2个Student对象和2个Teacher对象，统一放在数组中，并调用say方法。

public class PolyArr01 {
    public static void main(String[] args) {
        Person[] persons = new Person[5];
        persons[0] = new Person("jack",20);
        persons[1] = new Student("tom",18,97);
        persons[2] = new Student("jerry",19,66.5);
        persons[3] = new Teacher("scott",30,20000);
        persons[4] = new Teacher("harry",35,14000);

        for (int i = 0; i < persons.length; i++) {
            System.out.println(persons[i].say());
            //persons[i].say();//动态绑定机制
            //person[i]的编译类型是Person
            //运行类型根据实际情况
        }
    }
}

class Person {//父类
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String say() {
        return "name=" + getName()
                +", age=" + getAge();
    }
}

class Student extends Person{
    private double score;

    public Student(String name, int age, double score) {
        super(name, age);
        this.score = score;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }

    //重写父类say
    public String say() {
        return super.say() + ", score="+getScore();
    }
}

class Teacher extends Person {
    private double salary;

    public Teacher(String name, int age, double salary) {
        super(name, age);
        this.salary = salary;
    }

    public double getSalary() {
        return salary;
    }

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

    @Override
    public String say() {
        return super.say()+", salary="+getSalary();
    }
}

2、应用升级

应用实例升级：如何调用子类特有的方法，比如Teacher有一个teach，Student有一个study怎么调用?

        Person[] persons = new Person[5];
        persons[0] = new Person("jack",20);
        persons[1] = new Student("tom",18,97);
        persons[2] = new Student("jerry",19,66.5);
        persons[3] = new Teacher("scott",30,20000);
        persons[4] = new Teacher("harry",35,14000);
        
        //应用升级
        for (int i = 0; i < persons.length; i++) {
            if(persons[i] instanceof Student) {
                ((Student)persons[i]).study();
                //Student student = (Student)persons[i];向下转型
                //student.study();
            } else if(persons[i] instanceof Teacher) {
                ((Teacher)persons[i]).teach();
            } else {
                persons[i].say();
            }
        }

二、多态参数

方法定义的形参类型为父类类型，实参类型允许为子类类型。

• 定义员工类Employee，包含姓名和月工资[private]，以及计算年工资getAnnual的方法。普通员工和经理继承了员工，经理类多了奖金bonus属性和管理manage方法，普通员工类多了work方法，普通员工和经理类要求分别重写getAnnual方法。
• 测试类中添加一个方法showEmpAnnual(Employee e)，实现获取任何员工对象的年工资，并在main方法中调用该方法。
• 测试类中添加一个方法，testWork,如果是普通员工，则调用work方法，如果是经理，调用manage方法（这里写错了）

package com.lxhedu.poly_.polyParameter;

import com.lxhedu.extend_.improve_.Student;

public class PolyParameterTest {
    public static void main(String[] args) {
        Worker worker = new Worker("worker01",5000.5);
        Manager manager = new Manager("manager01",7000.5,1000);
        Test t1 = new Test();
        t1.showEmpAnnual(worker);
        t1.showEmpAnnual(manager);
        t1.testWork(worker);
        t1.testWork(manager);
    }
}
class Test {
    public void showEmpAnnual(Employee e) {
        System.out.println(e.getAnnual());
    }

    public void testWork(Employee e) {
        if(e instanceof Worker) {
            ((Worker)e).work();
        } else if(e instanceof Manager) {
            ((Manager)e).manage();
        }
    }
}
//Employee
class Employee {
    private String name;
    private double salary;

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

    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 String getAnnual() {
        return "月薪="+getSalary();
    }
}
//员工
class Worker extends Employee {
    public Worker(String name, double salary) {
        super(name, salary);
    }

    public void work() {
        System.out.println("员工"+super.getName()+"正在工作");
    }

    public String getAnnual() {
        return super.getAnnual()+",员工年薪="+getSalary()*12;
    }
}
//经理
class Manager extends Employee {
    private double bonus;

    public Manager(String name, double salary, double bonus) {
        super(name, salary);
        this.bonus = bonus;
    }

    public double getBonus() {
        return bonus;
    }

    public void setBonus(double bonus) {
        this.bonus = bonus;
    }

    public void manage() {
        System.out.println("经理"+super.getName()+"正在摸鱼");
    }

    public String getAnnual() {
        return super.getAnnual()+",经理年薪="+(getSalary()*12+getBonus());
    }
}