java_多态的应用_com.hspedu.poly-优快云博客

多态数组

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应用实例:现有一个继承结构如下：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，并调用每个对象

代码
Person类

package com.hspedu.poly_.polyarr_;

import javax.swing.*;

/**
 * @author:寰愬悏瓒�
 * @date:2024/12/14 version:1.0
 */
public class Person {
    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 +"\t" +  age;
    }
}

Student类

package com.hspedu.poly_.polyarr_;
import com.hspedu.poly_.polyarr_.Person;
/**
 * @author:寰愬悏瓒�
 * @date:2024/12/14 version:1.0
 */
public 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

    @Override
    public String say() {
        return "学生 " + super.say() + " score = " + score;
    }
}

Teacher类

package com.hspedu.poly_.polyarr_;


public 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;
    }
// 重写父类的say() 方法
    @Override
    public String say() {
        return "老师 " + super.say() + " salary= " + salary;
    }
}

PloyArray类

package com.hspedu.poly_.polyarr_;

/**
 * @author:寰愬悏瓒�
 * @date:2024/12/14 version:1.0
 */
public class PloyArray {
    public static void main(String[] args) {
/*
* 应用实例:现有一个继承结构如下：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，并调用每个对象
*/
        Person[] persons = new Person[5];
        persons[0] = new Person("jack",20);
        persons[1] = new Student("jack",18,100);
        persons[2] = new Student("smith",19, 30.1);
        persons[3] = new Teacher("scott",30,20000);
        persons[4] = new Teacher("king",50,25000);

//        循环遍历多态数组，调用say
        for(int i = 0; i < persons.length; i++ ){
//            person[i] 编译类型是 Person, 运行类型是 根据实际情况由JVM来判断
            System.out.println(persons[i].say());//动态绑定机制
        }
    }
}

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？
Teacher类增加teach()方法

//    特有的方法
    public void teach() {
        System.out.println("老师 " + getName() +" 正在上课");
    }

Student类增加study()方法

//    特有方法
    public void study() {
        System.out.println("学生 "  + getName() + " 正在学java");
    }

修改PloyArray类

package com.hspedu.poly_.polyarr_;


public class PloyArray {
    public static void main(String[] args) {
/*
* 应用实例:现有一个继承结构如下：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，并调用每个对象
*/
        Person[] persons = new Person[5];
        persons[0] = new Person("jack",20);
        persons[1] = new Student("mary",18,100);
        persons[2] = new Student("smith",19, 30.1);
        persons[3] = new Teacher("scott",30,20000);
        persons[4] = new Teacher("king",50,25000);

//        循环遍历多态数组，调用say
        for(int i = 0; i < persons.length; i++ ){
//            person[i] 编译类型是 Person, 运行类型是 根据实际情况由JVM来判断
            System.out.println(persons[i].say());//动态绑定机制
            if(persons[i] instanceof Student) { // 判断person[i] 的运行类型是不是 Student
                Student student = (Student)persons[i]; //向下转型
                student.study();
                // 也可以使用一条语句 ((Student)persons[i]).study();
            } else if(persons[i] instanceof Teacher) {
                Teacher teacher = (Teacher)persons[i];
                teacher.teach();
            } else if(persons[i] instanceof Person){

            } else {
                System.out.println("你的类型有问题，请自己检查...");
            }


        }
    }
}

多态参数

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代码：
Employee类

package com.hspedu.poly_.polyparameter_;


public class Employee {
   private String name;
   private double 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 Employee(String name, double salary) {

        this.name = name;
        this.salary = salary;
    }

    //得到年工资的方法
    public double getAnnual() {
        return 12*salary;
    }
}

Manager类

package com.hspedu.poly_.polyparameter_;

public 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 " + getName() + " is manageing");
    }

    //重写获取年薪方法
    @Override
    public double getAnnual() {
        return super.getAnnual()+bonus;
    }
}

Worker类

package com.hspedu.poly_.polyparameter_;


public class Worker extends Employee{
    public Worker(String name, double salary) {
        super(name, salary);
    }

    public void work() {
        System.out.println("员工 " + getName() + " is working");
    }

    //因为普通员工没有其它收入，则直接调用父类方法
    @Override
    public double getAnnual() {
        return super.getAnnual();
    }
}

Ployparameter类

package com.hspedu.poly_.polyparameter_;

import com.sun.corba.se.spi.orbutil.threadpool.Work;


public class Ployparameter {
    public static void main(String[] args) {
        Worker tom = new Worker("tom", 2500);
        Manager milian = new Manager("milian", 5000, 20000);
        Ployparameter ployparameter = new Ployparameter();

        ployparameter.showEmpAnnual(tom);
        ployparameter.showEmpAnnual(milian);

        ployparameter.testWork(tom);
        ployparameter.testWork(milian);

    }
    //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 [e.getAnnual()]
    public void showEmpAnnual(Employee e) {
        System.out.println(e.getAnnual());//动态绑定机制
    }
    //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，则调用 manage 方法
    public void testWork(Employee e) {
        if(e instanceof Worker) {
            ((Worker) e).work();  //向下转型
        } else if(e instanceof Manager) {
            ((Manager) e).manage(); //向下转型
        } else {
            System.out.println("你的类型不对，不做任何处理");
        }
    }
}