java新手笔记14 类继承示例

1.Person

package com.yfs.javase;

public class Person {

	private String name;
	private int age;
	private char sex;

	private void privateMehtod() {
		System.out.println("call privateMehtod()...");
	}

	public Person() {
		//System.out.println("创建Perosn对象...");
	}

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

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

	public void introduce() {
		System.out.println("I am Person....");
	}

	public String toString() {
		return "姓名：" + name + "  年龄 ：" + age + "  性别：" + sex;
	}

	public void speak() {
		System.out.println(name + " 工作了吗？");
	}

	public void sleep() {
		System.out.println(name + " 睡觉了吗？");
	}

	public void eat() {
		System.out.println(name + " 吃了吗？");
	}

	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 char getSex() {
		return sex;
	}

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

}

2.Student

package com.yfs.javase;

//实现代码重用  单继承
public class Student extends Person {// 继承Person

	private int score;

	@Override
	public void introduce() {
		System.out.println("I am student...");
	}
	// 覆盖 重写父类的方法
	@Override
	public String toString() {
		return super.toString() + "  成绩：" + score;
	}

	public int getScore() {
		return score;
	}

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

	public Student() {
		System.out.println("创建Student对象...");
	}

	// 扩展方法
	public void study() {
		System.out.println(getName() + " 在学习...");
	}

}

3.Teacher

package com.yfs.javase;

public class Teacher extends Person {
	private String job;

	public String getJob() {
		return job;
	}

	public void setJob(String job) {
		this.job = job;
	}

	@Override
	public void introduce() {
		System.out.println("I am teacher...");
	}

}

4.test1

package com.yfs.javase;

public class Demo1 {

	public static void main(String[] args) {
		Person p1 = new Person();
		p1.setName("张三");

		Student s1 = new Student();
		s1.setName("李四");

		Teacher t1 = new Teacher();
		t1.setName("王五");

		p1.speak();
		s1.speak();
		s1.study();
		t1.introduce();

		//s1 = t1;//类型不匹配  都是person子类
		//p1.study();  子类的方法属性不能访问
		//里氏替换
		Person p2 = s1;//父类的引用指向子类对象

		p2 = new Student();
		p2.setName("Tom");

		p2.sleep();
		//对象操作由声明类型决定
		//p2.study();//计算机技术人员
		//具体执行由对象决定  p2 中具体是什么对象

		p2 = new Teacher();

		//多态  方法覆盖
		p2.introduce();//父类声明的方法 子类覆盖父类的方法

	}

}

5.test2

package com.yfs.javase;

public class Demo2 {

	public static void main(String[] args) {
		Person p1 = new Person();
		p1.setName("张三");

		Student s1 = new Student();
		s1.setName("李四");

		Teacher t1 = new Teacher();
		t1.setName("王五");

		Person p2 = new Student();
		p2.setName("Tom");

		//变回去 强制转换
		Student s2 = (Student)p2;
		s2.study();

		//Teacher t2 = (Teacher)p2;

		//查看对象的类型 getClass()
		System.out.println(p2.getClass().getName());
		System.out.println(t1.getClass().getName());

		//s1 = p1;
		p1 = s1;
		System.out.println(p1);
		System.out.println(s1);
		s1.setAge(20);
		p1.setSex('男');
		System.out.println(p1);
		System.out.println(s1);
		//p1.study();

	}

}