30天学会JAVA—练习题(2021韩顺平)——Day10

class Person{
   
	private String name;
	private char sex;
	private int age;
	
	public Person(String name, char sex, int age) {
   
		super();
		this.name = name;
		this.sex = sex;
		this.age = age;
	}

	public String getName() {
   
		return name;
	}

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

	public char getSex() {
   
		return sex;
	}

	public void setSex(char sex) {
   
		this.sex = sex;
	}

	public int getAge() {
   
		return age;
	}

	public void setAge(int age) {
   
		this.age = age;
	}
	
	public String play(){
   
		return name + "爱玩";
	}
	
	public void showInfo(){
   
		System.out.println("姓名:" + getName()) ;
		System.out.println("年龄:" + getAge()) ;
		System.out.println("性别:" + getSex()) ;
	}
}

class Student extends Person{
   

	private String stu_id;	
	public Student(String name, char sex, int age, String stu_id) {
   
		super(name, sex, age);
		this.stu_id = stu_id;
	}

	public String getStu_id() {
   
		return stu_id;
	}

	public void setStu_id(String stu_id) {
   
		this.stu_id = stu_id;
	}
	
	public void study(){
   
		System.out.println("我承诺,我会好好学习");
	}
	
	@Override
	public String play() {
   
		System.out.println("----------------");
		System.out.println(getName()+ "爱玩足球");
		return getName();

	}
	@Override
	public void showInfo() {
   
		System.out.println("学生的信息:");
		super.showInfo();
		System.out.println("学号:" + stu_id);
	}
}

class Teacher extends Person{
   
	private int work_age;
	
	public Teacher(String name, char sex, int age, int work_age) {
   
		super(name, sex, age);
		this.work_age = work_age;
	}

	public int getWork_age() {
   
		return work_age;
	}

	public void setWork_age(int work_age) {
   
		this.work_age = work_age;
	}
	
	public void teach(){
   
		System.out.println("我承诺,我会认真教学");
	}
	
	@Override
	public String play() {
   
		System.out.println("----------------");
		System.out.println(getName()+ "爱玩象棋");
		return getName();
	}
	
	@Override
	public void showInfo() {
   
		System.out.println("老师的信息:");
		super.showInfo();
		System.out.println("工龄:" + work_age);
	}
}


public class Test {
   	
	public static void main(String[] args) {
   
		//定义多态数组
		Person[] persons = new Person[4];
		persons[0] = new Teacher("张飞", '男', 30, 5);
		persons[1] = new Teacher("张三", '男', 45, 7);
		persons[2] = new Student("lili", '女', 12, "123");
		persons[3] = new Student("aby", '男', 16, "456");
		
		for(int i = 0; i < persons.length-1; i++){
   //冒泡排序
			for(int j = 0; j < persons.length-1-i;j++){
   
				if(persons[j].getAge() < persons[j+1].getAge()){
   
					Person temp = persons[j];
					persons[j] = persons[j+1];
					persons[j+1] = temp;
				}
			}	
		}
		
			for(int i = 0 ; i < persons.length; i++){
   
				if(persons[i] instanceof Student){
   //判断类型 并向下转型
					Student s = (Student) persons[i];
					s.showInfo();
					s.study();
					s.play();
				}else if(persons[i] instanceof Teacher){
   
					Teacher t = (Teacher) persons[i];
					t.showInfo();
					t.teach();
					t.play();
			}else if(persons[i] instanceof Teacher){
   
				Person p = (Person) persons[i];
				p.showInfo();
			}else{
   
				System.out.println("输入类型有误,请重新输入");
			}
		}				
	}		
}

我是A类
hahah我是B类的有参构造
我是C类的有参构造
我是C类的无参构造

• super()，即为继承父类的构造函数
• 继承之后，都是先执行父类的无参构造，再执行自己的有参构造
  

15.多态

>多态定义：
方法或对象具有多种形态，是面向对象（OOP）的第三大特征，是建立在封装和继承基础之上的

>多态具体体现：

1. 方法多态：重载与重写
2. 对象多态：对象的编译类型和运行类型可以不一致，编译类型在定义时就确定，不能变化；对象的运行类型时可以变化的，可通过getClass()来查看运行类型【左编译，右运行】

16.动态绑定机制

-调用对象<mark>方法</mark>时，该方***和对象的<mark>内存地址/运行类型</mark>（等号右边）绑定
-调用对象属性时，没有动态绑定，哪里声明哪里使用