Java中的动态绑定机制

package JAVA面向对象中级部分.encapsulationAndInherit.binding;
public class DynamicBinding {
    public static void main(String[] args) {
        A a  = new B();//向上转型
        //当注释了B类中的sum()方法和sum1()方法结果变为了30和20
        System.out.println(a.sum());//40 --》30
        System.out.println(a.sum1());//30 --》20
    }
}
class A{//父类
    public int i = 10;
    //由于调用方法时，方法会和该对象的内存地址（也就是运行类型）绑定
    //由于运行类型是B，所以查找是从B类方法开始查找，要因为B类中的getI()方法，直接返回属性i,属性没有动态绑定机制，因此直接返回20
    public int sum(){
        return getI()+10;
    }
    //方法是有动态绑定机制，所以查找时，先从子类B查找，由于B类没有sum1方法，
    //继承查找父类，父类有则调用sum1方法，要因为sum1方法返回是属性i，属性没有动态绑定机制直接返回i的值，所以是20
    public int sum1(){
        return i+10;
    }
    public int getI(){
        return i;
    }
}
class B extends A {
    public int i = 20;
//    public int sum(){
//        return i+20;
//    }
//
//    public int sum1(){
//        return i+10;
//    }
    public int getI(){
        return i;
    }
}

package JAVA面向对象中级部分.encapsulationAndInherit.ployArray;
public class Person {
    private String name;
    private int age;
    public Person() {
    }
    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+"\t年龄:"+age;
    }
}
package JAVA面向对象中级部分.encapsulationAndInherit.ployArray;
public class Student extends  Person{
    private double score;
    public Student(String name,int age) {
        this.setName(name);
        this.setAge(age);
    }
    public Student(String name,int age,double score){
        //注意在构造器中使用super和this调用构造器完成初始化，两者只能出一个并且放在第一条语句
        super(name,age);
//        this(name,age);
        this.score =score;
    }
    public String say(){
        return super.say()+"\t成绩:"+score;
    }
    public void study(){
        System.out.println("学生:"+getName()+"正在学习JAVA课程！");
    }
}
package JAVA面向对象中级部分.encapsulationAndInherit.ployArray;
public class Teacher extends  Person{
    private double salary;
    public Teacher(String name,int  age) {
        this.setName(name);
        this.setAge(age);
    }
    public Teacher(String name,int age,double salary){
        super(name,age);
        this.salary = salary;
    }
    public String say(){
        return super.say()+"\tsalary:"+salary;
    }
    public void teach(){
        System.out.println("老师:"+getName()+"正在教JAVA课程！");
    }
}
package JAVA面向对象中级部分.encapsulationAndInherit.ployArray;
public class PloyArray {
    public static void main(String[] args) {
        Person[] people = new Person[5];
        people[0] = new Person("海康",20);
        people[1] = new Student("湛江",18,99);
        people[2] = new Student("南宁",20,99.9);
        people[3] = new Teacher("西安",21,21688);
        people[4] = new Teacher("广州",22,22168);
        //循环遍历多态数组，调用say
        for (int i = 0; i < people.length; i++) {
            //person[i]编译类型是Person，运行类型是根据实际情况有JV来判断
//            System.out.println(people[i].say());//动态绑定机制
            if (people[i] instanceof Student){
                Student student = (Student) people[i];
                student.study();
            }else if (people[i] instanceof  Teacher){
                Teacher teacher = (Teacher) people[i];
                teacher.teach();
            }else {
                System.out.println(people[i].say());//在类型转换时，范围大的一定要放在后面，要不大的对小范围有接收作用
            }
        }
    }
}

public class PloyParameter {
    public static void main(String[] args) {
        Worker worker = new Worker("海康", 18168);
        testWork(worker);
        double v = showEmpAnnual(worker);
        System.out.println(v);
        System.out.println("=================经理===============");
        Manager manager = new Manager("明天", 81688, 100000);
        testWork(manager);
        double v1 = showEmpAnnual(manager);
        System.out.println(v1);
    }
    public static double showEmpAnnual(Employee employee){
        return employee.getAnnual();
    }
    public static void testWork(Employee employee){
        if (employee instanceof Worker){
            Worker worker = (Worker) employee;
            worker.work();
        }else if (employee instanceof Manager){
            Manager manager = (Manager) employee;
            manager.manage();
        }else {
            System.out.println("您输入的类型有误！");
        }
    }
}

public class Employee {
    private String name;
    private double salary;
    public Employee() {
    }
    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;
    }
    //计算年工资getAnnual方法
    public double getAnnual(){
        return salary*12;
    }
}

public class Worker  extends Employee{
    public Worker() {
    }
    public Worker(String name, double salary) {
        super(name, salary);
    }
    //普通员工work方法
    public void work(){
        System.out.println("普通员工打工干活");
    }
    public double getAnnual(){
        return getSalary()*12;
    }
}

public class Manager extends Employee{
    private double bonus;
    public Manager(String name,double salary){
        super(name,salary);
    }
    public Manager(double bonus) {
        this.bonus = bonus;
    }
    public Manager(String name, double salary, double bonus) {
        super(name, salary);
        this.bonus = bonus;
    }
    //管理方法
    public void manage(){
        System.out.println("经理放屁了");
    }
    public double getAnnual(){
        return getSalary()*12 + bonus;
    }
}