1、继承示例
1.1
创建Pet(宠物)父类
// 创建Pet(宠物)父类
public class Pet {
//创建父类私有属性
private String name;
private int age;
private int health;
private String love;
public Pet(){
//System.out.println("父类无参构造方法");
}
public Pet(String name,int age,int health,String love){
this.name = name;
this.age = age;
this.health = health;
this.love = love;
//System.out.println("父类有参构造方法");
}
//get方法
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 int getHealth() {
return health;
}
//set方法
public void setHealth(int health) {
this.health = health;
}
public String getLove() {
return love;
}
public void setLove(String love) {
this.love = love;
}
// 父类中的print（打印）方法
public void print(){
System.out.println(name+"\t"+age+"\t"+health+"\t"+love);
}
// 父类中的shout（叫声）方法
public void shout(){
System.out.println("宠物的叫声！");
}
} 创建Dog（宠物>狗）子类extends关键字
// 创建Dog（宠物>狗）子类继承父类Pet
public class Dog extends Pet {
// 狗类特有的strain（品种）属性
public String strain;
public Dog() {
// System.out.println("子类无参构造方法");
}
public Dog(String name, int age, int health, String love,String strain) {
// super关键字：引用父类中的属性
super(name, age, health, love);
this.strain = strain;
// System.out.println("子类有参构造方法");
}
// 子类get方法
public String getStrain() {
return strain;
}
// 子类set方法
public void setStrain(String strain) {
this.strain = strain;
}
// 父类print方法重写
public void print(){
System.out.println(super.getName()+"\t"+super.getAge()+"\t"+super.getHealth()+"\t"+super.getLove()+"\t"+strain);
}
// 父类shout方法重写
// public void shout(){
//
// System.out.println("名叫"+this.getName()+"小狗汪汪的叫声！");
//
// }
//
}// 创建PetDemo测试类
public class PetDemo {
public static void main(String[] args) {
Dog dog = new Dog("旺财", 2, 100, "友爱", "泰迪");
//
// dog.setName("旺财");
//
// dog.strain="泰迪";
//
// dog.setAge(2);
//
// dog.setHealth(100);
//
// dog.setLove("友爱");
//
// System.out.println(dog.getName() + "\t" + dog.strain + "\t"
//
// + dog.getAge() + "\t" + dog.getHealth() + "\t" + dog.getLove());
dog.print();
// Penguin penguin = new Penguin();
// Pet pet1 = new Dog();
// Pet pet2 = new Penguin();
// pet1.shout();
// pet2.shout();
// Petshop petshop = new Petshop();
// Pet pet3 = petshop.BuyPet();
// pet3.shout();
// if(pet3 instanceof Dog){
// Dog dog1 = (Dog)pet3;
// System.out.println(dog1.getStrain());
// }else{
// Penguin penguin1 = (Penguin)pet3;
// System.out.println(penguin1.getSex());
// }
// Pet dog = new Dog("旺财",12,100,"友爱","泰迪");
//
// dog.shout();
//
}
} 结果验证一：
旺财2100友爱泰迪
结果验证二：去掉Dog类中super（）；中内容
null00null泰迪
2、多态示例一
“+”：可以表示加法运算符；可以表示拼接运算符。
2.1
//创建Pet(宠物)父类
public class Pet {
//创建父类私有属性
private String name;
private int age;
private int health;
private String love;
public Pet(){
//System.out.println("父类无参构造方法");
}
public Pet(String name,int age,int health,String love){
this.name = name;
this.age = age;
this.health = health;
this.love = love;
//System.out.println("父类有参构造方法");
}
//get方法
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 int getHealth() {
return health;
}
//set方法
public void setHealth(int health) {
this.health = health;
}
public String getLove() {
return love;
}
public void setLove(String love) {
this.love = love;
}
// 父类中的print（打印）方法
public void print(){
System.out.println(name+"\t"+age+"\t"+health+"\t"+love);
}
// 父类中的shout（叫声）方法
public void shout(){
System.out.println("宠物的叫声！");
}
}创建Dog（宠物>狗）子类继承父类Pet
// 创建Dog（宠物>狗）子类继承父类Pet
public class Dog extends Pet {
// 狗类特有的strain（品种）属性
public String strain;
public Dog() {
// System.out.println("子类无参构造方法");
}
public Dog(String name, int age, int health, String love,String strain) {
// super关键字：引用父类中的属性
super(name, age, health, love);
this.strain = strain;
// System.out.println("子类有参构造方法");
}
// 子类get方法
public String getStrain() {
return strain;
}
// 子类set方法
public void setStrain(String strain) {
this.strain = strain;
}
// 父类print方法重写
//
// public void print(){
//
// System.out.println(super.getName()+"\t"+super.getAge()+"\t"+super.getHealth()+"\t"+super.getLove()+"\t"+strain);
// }
// 父类shout方法重写
public void shout(){
System.out.println("名叫"+this.getName()+"小狗汪汪的叫声！");
}
}// 创建PetDemo测试类
public class PetDemo {
public static void main(String[] args) {
// Dog dog = new Dog("旺财",2,100,"友爱","泰迪");
//dog.setName("旺财");
//dog.strain="泰迪";
//dog.setAge(2);
//dog.setHealth(100);
//dog.setLove("友爱");
// System.out.println(dog.getName()+"\t"+dog.strain+"\t"+dog.getAge()+"\t"+dog.getHealth()+"\t"+dog.getLove());
// dog.print();
// Penguin penguin = new Penguin();
// Pet pet1 = new Dog();
// Pet pet2 = new Penguin();
// pet1.shout();
// pet2.shout();
// Petshop petshop = new Petshop();
// Pet pet3 = petshop.BuyPet();
// pet3.shout();
// if(pet3 instanceof Dog){
// Dog dog1 = (Dog)pet3;
// System.out.println(dog1.getStrain());
// }else{
// Penguin penguin1 = (Penguin)pet3;
// System.out.println(penguin1.getSex());
// }
Pet dog = new Dog("旺财",12,100,"友爱","泰迪");
dog.shout();
}
}结果验证：
名叫旺财小狗汪汪的叫声！
2.2 多态的示例
创建Pet(宠物)父类
//创建Pet(宠物)父类
public class Pet {
//创建父类私有属性
private String name;
private int age;
private int health;
private String love;
public Pet(){
//System.out.println("父类无参构造方法");
}
public Pet(String name,int age,int health,String love){
this.name = name;
this.age = age;
this.health = health;
this.love = love;
//System.out.println("父类有参构造方法");
}
//get方法
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 int getHealth() {
return health;
}
//set方法
public void setHealth(int health) {
this.health = health;
}
public String getLove() {
return love;
}
public void setLove(String love) {
this.love = love;
}
// 父类中的print（打印）方法
public void print(){
System.out.println(name+"\t"+age+"\t"+health+"\t"+love);
}
// 父类中的shout（叫声）方法
public void shout(){
System.out.println("宠物的叫声！");
}
}创建Dog（宠物>狗）子类继承父类Pet
// 创建Dog（宠物>狗）子类继承父类Pet
public class Dog extends Pet {
// 狗类特有的strain（品种）属性
public String strain;
public Dog() {
// System.out.println("子类无参构造方法");
}
public Dog(String name, int age, int health, String love,String strain) {
// super关键字：引用父类中的属性
super(name, age, health, love);
this.strain = strain;
// System.out.println("子类有参构造方法");
}
// 子类get方法
public String getStrain() {
return strain;
}
// 子类set方法
public void setStrain(String strain) {
this.strain = strain;
}
// 父类print方法重写
//
// public void print(){
//
// System.out.println(super.getName()+"\t"+super.getAge()+"\t"+super.getHealth()+"\t"+super.getLove()+"\t"+strain);
// }
// 父类shout方法重写
public void shout(){
System.out.println("名叫"+this.getName()+"小狗汪汪的叫声！");
}
}创建Penguin（宠物>企鹅）类
// 创建Penguin（宠物>企鹅）类
public class Penguin extends Pet{
// 企鹅sex（性别）特有属性
public String sex;
// 子类get方法
public String getSex() {
return sex;
}
// 子类set方法
public void setSex(String sex) {
this.sex = sex;
}
// 父类shout方法重写
public void shout(){
System.out.println("名叫"+this.getName()+"企鹅喵喵的叫声！");
}
}创建Petshop（提供购买的方法）类
//创建Petshop（提供购买的方法）类
import java.util.Scanner;
public class Petshop {
// 创建BuyPet方法
public Pet BuyPet(){
// 定义pet变量的初始值为null(空)
Pet pet = null;
// 提示用户的输入数字
System.out.println("请输入您要购买的宠物：1.小狗 2.小企鹅");
// 获取用户的输入存取到buypet变量中
Scanner input = new Scanner(System.in);
int buyPet = input.nextInt();
// switch判断用户输入数字
switch(buyPet){
case 1://当用户输入数字1，则宠物为小狗
pet = new Dog("旺财",2,100,"友爱","泰迪");
break;
case 2://当用户输入数字2，则宠物为小企鹅
pet = new Penguin();
break;
default:
break;
}
return pet;
}
}创建PetDemo测试类
//创建PetDemo测试类
public class PetDemo {
public static void main(String[] args) {
// Dog dog = new Dog("旺财",2,100,"友爱","泰迪");
//dog.setName("旺财");
//dog.strain="泰迪";
//dog.setAge(2);
//dog.setHealth(100);
//dog.setLove("友爱");
// System.out.println(dog.getName()+"\t"+dog.strain+"\t"+dog.getAge()+"\t"+dog.getHealth()+"\t"+dog.getLove());
// dog.print();
// Penguin penguin = new Penguin();
// Pet pet1 = new Dog();
// Pet pet2 = new Penguin();
// pet1.shout();
// pet2.shout();
Petshop petshop = new Petshop();
// 调用子类方法重写父类
Pet pet3 = petshop.BuyPet();
// 实现宠物叫声的多态，抽象父类的引用指向子类的对象，实现多态
pet3.shout();
// if(pet3 instanceof Dog){
//
// Dog dog1 = (Dog)pet3;
//
// System.out.println(dog1.getStrain());
//
// }else{
//
// Penguin penguin1 = (Penguin)pet3;
//
// System.out.println(penguin1.getSex());
//
// }
//
// Pet dog = new Dog("旺财",12,100,"友爱","泰迪");
//
// dog.shout();
//
}
}结果验证一：
请输入您要购买的宠物：1.小狗 2.小企鹅
1
名叫旺财小狗汪汪的叫声！
结果验证二：
请输入您要购买的宠物：1.小狗 2.小企鹅
2
名叫null企鹅喵喵的叫声！
3、instanceof关键字
此关键字访问子类中特有的属性
public class PetDemo {
public static void main(String[] args) {
// Dog dog = new Dog("旺财",2,100,"友爱","泰迪");
//dog.setName("旺财");
//dog.strain="泰迪";
//dog.setAge(2);
//dog.setHealth(100);
//dog.setLove("友爱");
// System.out.println(dog.getName()+"\t"+dog.strain+"\t"+dog.getAge()+"\t"+dog.getHealth()+"\t"+dog.getLove());
// dog.print();
// Penguin penguin = new Penguin();
// Pet pet1 = new Dog();
// Pet pet2 = new Penguin();
// pet1.shout();
// pet2.shout();
Petshop petshop = new Petshop();
// 调用子类方法重写父类
Pet pet3 = petshop.BuyPet();
// 实现宠物叫声的多态，抽象父类的引用指向子类的对象，实现多态
pet3.shout();
if(pet3 instanceof Dog){
Dog dog1 = (Dog)pet3;
System.out.println(dog1.getStrain());
}else{
Penguin penguin1 = (Penguin)pet3;
System.out.println(penguin1.getSex());
}
// Pet dog = new Dog("旺财",12,100,"友爱","泰迪");
//
// dog.shout();
//
}
}结果验证一：
请输入您要购买的宠物：1.小狗 2.小企鹅
1
名叫旺财小狗汪汪的叫声！
泰迪
结果验证二：
请输入您要购买的宠物：1.小狗 2.小企鹅
2
名叫null企鹅喵喵的叫声！
null