韩顺平第八章多态的题

package overload;

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 "姓名" + name + "年龄" + age;
    }
}

以上为父类

package overload;

public class Student extends Person {
    private int id;
    private double score;

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

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }
    public String say(){
       // return "学生的" + super.say() + "id为" + id + "分数为" + score;
        return "学生的" +getName() +"年龄" + getAge() + "id为" + id + "分数为" + score;
    }
    public void study(){
        System.out.println("学生的study方法被调用");
    }
}

以上为子类学生类

package overload;

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;
    }

    public String say() {
        return "老师的" + super.say() + "薪水为" + salary;
    }
    public void teach(){
        System.out.println("老师的teach方法被调用");
    }
}

以上为子类教师类

package overload;

public class Test {
    public static void main(String[] args) {
        Person[] people = new Person[5];
        people[0]=new Person("JAKE",18);
        people[1]= new Student("ZJH",22,18076120,99.0);
      //编译类型  Person person=new Student("ZJH",22,18076120,99.0);运行类型
        people[2]=new Student("nihao",222,18076121,100);
        people[3]=new Teacher("milan",100,1000);
        people[4]=new Teacher("ggg",55,80000);

        for ( int i = 0; i < people.length; i++) {
           //以下为调用子类重写的方法，利用动态绑定机制
           System.out.println(people[i].say());
            //以下为通过父类调用子类特有的方法
            if(people[i] instanceof Student ){
                ((Student)people[i]).study();
//                Student student = (Student)people[i];
//                student.study();
            }else if(people[i] instanceof Teacher){
                ((Teacher)people[i]).teach();
//                Teacher teacher = (Teacher)people[i];
//                teacher.teach();
            }else{
                System.out.println("请重新输入");
            }
        }
        //向上引用 Animal animal = new Cat();
       // people[1].teach();//错误，因为Personl类中没有teach方法，编译类型不通过，
                          // 采用向下转型的方法   Cat cat = (Cat)animal

    }
}

主方法，注意数组里放置的是对象，注意用多态来解决调用子类重写的方法（动态绑定机制）和调用子类特有的方法的问题（向下转型）