第十四天（继承）

最新推荐文章于 2023-03-07 16:44:12 发布

原创最新推荐文章于 2023-03-07 16:44:12 发布 · 1.2k 阅读

4 ·

CC 4.0 BY-SA版权

第一阶段同时被 2 个专栏收录

15 篇文章

订阅专栏

JAVA学习

14 篇文章

订阅专栏

本文通过多个示例深入探讨了Java中继承与多态的概念，包括不同类型的构造方法调用、super关键字的使用、方法覆盖及重写等关键知识点，并提供了具体的代码案例。

1. （继承、this 和super 关键字）有以下代码

class Super{

public Super(){

System.out.println("Super()");

}

public Super(String str){

System.out.println("Super(String)");

}

class Sub extends Super{

public Sub(){

System.out.println("Sub()");

}

public Sub(int i){

this();

System.out.println("Sub(int)");

}

public Sub(String str){

super(str);

System.out.println("Sub(String)");

}

public class TestSuperSub{

public static void main(String args[]){

Sub s1 = new Sub();

Sub s2 = new Sub(10);

Sub s3 = new Sub("hello");

}

写出该程序运行的结果。

输出结果：

Super()

Sub()

Super()

Sub()

Sub(int)

Super(String)

Sub(String)

2. （super）看下面代码，写出程序运行的结果

class Super{

public void m1(){

System.out.println("m1() in Super" );

}

public void m2(){

System.out.println("m2() in Super" );

}

class Sub extends Super{

public void m1(){

System.out.println("m1() in Sub");

super.m1();

}

public class TestSuperSub{

public static void main(String args[]){

Sub s = new Sub();

s.m1();

s.m2();

}

输出结果：

m1() in Sub

m1() in Super

m2() in Super

3、（继承、对象构造过程）有以下代码

class Meal{

public Meal(){

System.out.println("Meal()");

}

class Lunch extends Meal{

public Lunch(){

System.out.println("Lunch()");

}

class Vegetable {

public Vegetable(){

System.out.println("Vegetable()");

}

class Potato extends Vegetable{

public Potato(){

System.out.println("Potato()");

}

class Tomato extends Vegetable{

public Tomato(){

System.out.println("Tomato()");

}

class Meat{

public Meat(){

System.out.println("Meat()");

}

class Sandwichextends Lunch{

Potato p = new Potato();

Meat m = new Meat();

Tomato t = new Tomato();

public Sandwich(){

System.out.println("Sandwich()");

}

public class TestSandwich{

public static void main(String args[]){

Sandwich s = new Sandwich();

}

写出这段代码的输出结果。

输出结果：

Meal()

Lunch()

Vegetable()

Potato()

Meat()

Vegetable()

Tomato()

Sandwich()

4 *（方法覆盖）有如下代码

class Super{

int method(){return 0;}

}

class Sub extends Super{

// 1

}

在//1 处，能编译通过的代码为：

A. public int method(){return 0;}

B. void method(){}

C. void method(int n){}

5. *（方法覆盖）有如下代码

class Super{

private void method(){}

}

class Sub extends Super{

//1

}

在//1 处，能编译通过的代码为：

A. public int method(){return 0;}

B. void method(){}

C. void method(int n){}

D. private void method(){}

ABCD

package day14;
 
public class Demo14_3 {
        public static void main(String[] args) {
                Student stu=new Student("张三",23,"江苏","214000","1381402222");
                System.out.println(stu.getName());
                System.out.println(stu.getAge());
                System.out.println(stu.getAdress());
                System.out.println(stu.getZipCode());
                System.out.println(stu.getMobile());
                stu.getPostAddress();
        }
}
class Student{
        private String name;
        private int age;
        private String adress;
        private String zipCode;
        private String mobile;
        public Student(String name,int age,String adress,String zipCode,String mobile){
                this.name=name;
                this.age=age;
                this.adress=adress;
                this.zipCode=zipCode;
                this.mobile=mobile;
        }
        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 getAdress() {
                return adress;
        }
        public void setAdress(String adress) {
                this.adress = adress;
        }
        public String getZipCode() {
                return zipCode;
        }
        public void setZipCode(String zipCode) {
                this.zipCode = zipCode;
        }
        public String getMobile() {
                return mobile;
        }
        public void setMobile(String mobile) {
                this.mobile = mobile;
        }
        public void getPostAddress(){
                System.out.println(adress+" "+zipCode);
        }
}

class Account{
        private int id;
        private double balance;
        private String password;
        public int getId() {
                return id;
        }
        public void setId(int id) {
                this.id = id;
        }
        public double getBalance() {
                return balance;
        }
        public void setBalance(double balance) {
                this.balance = balance;
        }
        public String getPassword() {
                return null;
        }
        public void setPassword(String password) {
                if(password.length()!=6){
                        return;
                }
                this.password = password;
        }
}
 
class SaveAccount extends Account{
        private double interestRate;
 
        public double getInterestRate() {
                return interestRate;
        }
 
        public void setInterestRate(double interestRate) {
                if(interestRate>0 && interestRate<10/100){
                        this.interestRate = interestRate;
                }
        }
}
 
class CreditAccount extends Account{
        private double creditLine;
}

8、描述不同的动物不同的叫法

1：定义动物类

有名字，有吃和叫的方法

2：定义狗继承动物重写父类吃和叫的方法

3：定义猫继承动物重写父类吃和叫的方法

要求：通过主函数调用相关函数和属性信息信息

class Animal {
        private String name;
 
        public String getName() {
                return name;
        }
 
        public void setName(String name) {
                this.name = name;
        }
         
        public void eat(){
                System.out.println(name+"吃東西");
        }
         
        public void call(){
                System.out.println(name+"在叫...");
        }
}
 
class Dog extends Animal{
        @Override
        public void eat() {
                System.out.println(super.getName()+"在吃東西");
        }
         
        @Override
        public void call() {
                System.out.println(super.getName()+"在叫....");
        }
}
 
class Cat extends Animal{
        @Override
        public void eat() {
                System.out.println(super.getName()+"在吃東西");
        }
         
        @Override
        public void call() {
                System.out.println(super.getName()+"在叫....");
        }
}
 
public class TestAnimal{
        public static void main(String[] args) {
                Animal a1 = new Dog();
                a1.setName("夠");
                a1.eat();
                a1.call();
                System.out.println();
                Animal a2 = new Dog();
                a2.setName("貓");
                a2.eat();
                a2.call();
        }
}

9、某公司的雇员分为以下若干类：

Employee：这是所有员工总的父类，

属性：员工的姓名和生日月份。

方法：getSalary(int month) 根据参数月份来确定工资，如果该月员工过生日，则公司会额外奖励100元。

SalariedEmployee：Employee的子类，拿固定工资的员工。

属性：月薪

HourlyEmployee：Employee的子类，按小时拿工资的员工，每月工作超出160小时的部分按照1.5倍工资发放

属性：每小时的工资、每月工作的小时数

SalesEmployee：Employee的子类，销售人员，工资由月销售额和提成率决定

属性：月销售额、提成率

BasePlusSalesEmployee：SalesEmployee的子类，有固定底薪的销售人员，工资由底薪加上销售提成部分

属性：底薪。

实现：1、李易峰固定员工，月薪3000，生日月份2月，工作180小时，获取工资多少

2、张子明小时工，每小时25，工作180小时，获取工资多少

3、林肯销售人员月销售额30万，提成0.3% 获取工资

4、阳光固定底薪销售人员底薪1500 ，销售20万，提成0.2% 获取工资

public class TestEmployee {
 
        public static void main(String[] args) {
                SalariedEmployee se = new SalariedEmployee();
                se.setName("李易峰");
                se.setSalary(3000);
                se.setBirthMonth(2);
                se.getSalary(2);
 
                HourlyEmployee he = new HourlyEmployee();
                he.setName("张子明");
                he.setHourSalary(25);
                he.setHours(180);
                he.getSalary();
 
                SalesEmployee sae = new SalesEmployee();
                sae.setName("林肯");
                sae.setMonthsales(300000);
                sae.setRoyalRate(0.003);
                sae.getSalary();
 
                BasePlusSalesEmployee bse = new BasePlusSalesEmployee();
                bse.setName("阳光");
                bse.setBaseSalary(1500);
                bse.setMonthsales(200000);
                bse.setRoyalRate(0.002);
                bse.getSalary();
        }
}
 
class Employee {
        String name;
        int birthMonth;
        double salary;
 
        public String getName() {
                return name;
        }
 
        public void setName(String name) {
                this.name = name;
        }
 
        public int getBirthMonth() {
                return birthMonth;
        }
 
        public void setBirthMonth(int birthMonth) {
                this.birthMonth = birthMonth;
        }
 
        public void setSalary(double salary) {
                this.salary = salary;
        }
 
        public void getSalary(int month) {
                if (birthMonth == month) {
                        System.out.println(name + "当月月薪" + (salary + 100));
                }
        }
}
 
class SalariedEmployee extends Employee {
 
}
 
class HourlyEmployee extends Employee {
        double hourSalary;
        double hours;
        double salary;
 
        public double getHourSalary() {
                return hourSalary;
        }
 
        public void setHourSalary(double hourSalary) {
                this.hourSalary = hourSalary;
        }
 
        public double getHours() {
                return hours;
        }
 
        public void setHours(double hours) {
                this.hours = hours;
        }
 
        public void setSalary(double salary) {
                this.salary = salary;
        }
 
        public void getSalary() {
                if (hours > 160) {
                        System.out.println(name + "月薪为" + (hourSalary * 160 + ((hours - 160) * hourSalary * 1.5)));
                } else {
                        System.out.println(name + "月薪为" + hourSalary * hours);
                }
 
        }
}
 
class SalesEmployee extends Employee {
        double monthsales;
        double royalRate;
 
        public double getMonthsales() {
                return monthsales;
        }
 
        public void setMonthsales(double monthsales) {
                this.monthsales = monthsales;
        }
 
        public double getRoyalRate() {
                return royalRate;
        }
 
        public void setRoyalRate(double royalRate) {
                this.royalRate = royalRate;
 
        }
 
        public void setSalary(double salary) {
                this.salary = salary;
        }
 
        public void getSalary() {
                System.out.println(name + "月薪为" + monthsales * royalRate);
        }
 
}
 
class BasePlusSalesEmployee extends SalesEmployee {
        double baseSalary;
 
        public double getBaseSalary() {
                return baseSalary;
        }
 
        public void setBaseSalary(double baseSalary) {
                this.baseSalary = baseSalary;
        }
 
        public void getSalary() {
                System.out.println(name + "月薪为" + baseSalary + monthsales * royalRate);
        }
}