面向对象编程练习题
第一题
定义一个 Person 类 {name, age, job}，初始化 Person 对象数组，有 3 个 person 对象，并按照 age 从大到小进行排序，提示，使用冒泡排序。
package com.hspedu.homework;
import java.util.SortedMap;
public class Homework01 {
public static void main(String[] args) {
Person[] persons = new Person[3];
persons[0] = new Person("Tom", 20, "student");
persons[1] = new Person("Jack", 18, "worker");
persons[2] = new Person("Smith", 19, "singer");
//输出当前对象数组
System.out.println("当前对象数组:");
for(int i = 0; i < persons.length; i++){
System.out.println(persons[i]);
}
//使用冒泡排序
for(int i = 0; i < persons.length - 1; i++){
for(int j = 0; j <persons.length - i - 1; j++){
if(persons[j].getAge() < persons[j + 1].getAge()){
Person temp = persons[j];
persons[j] = persons[j + 1];
persons[j + 1] = temp;
}
}
}
System.out.println("对象数组按照年龄(从大到小)排序后：");
for(int i = 0; i < persons.length; i++){
System.out.println(persons[i]);
}
}
}
class Person{
private String name;
private int age;
private String job;
public Person(String name, int age, String job) {
this.name = name;
this.age = age;
this.job = job;
}
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 getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
", job='" + job + '\'' +
'}';
}
}
第二题
写出四种访问修饰符和各自的访问权限。
第三题
编写老师类。
Homework03.java：
package com.hspedu.homework;
public class Homework03 {
public static void main(String[] args) {
Teacher[] teachers = new Teacher[3];
teachers[0] = new Professor("John", 50, "教授", 30000, 1.3);
teachers[1] = new FProfessor("Tom", 40, "副教授", 20000, 1.2);
teachers[2] = new JiangShi("Mary", 30, "讲师", 10000, 1.1);
for(int i = 0; i < teachers.length; i++){
teachers[i].introduce();
}
}
}
Teacher.java：
package com.hspedu.homework;
public class Teacher{
private String name;
private int age;
private String post;
private double salary;
private double grade;
public Teacher(String name, int age, String post, double salary, double grade) {
this.name = name;
this.age = age;
this.post = post;
this.salary = salary;
this.grade = grade;
}
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 getPost() {
return post;
}
public void setPost(String post) {
this.post = post;
}
public double getSalary() {
return salary;
}
public void setSalary(double salary) {
this.salary = salary;
}
public double getGrade() {
return grade;
}
public void setGrade(double grade) {
this.grade = grade;
}
@Override
public String toString() {
return "Teacher{" +
"name='" + name + '\'' +
", age=" + age +
", post='" + post + '\'' +
", salary=" + salary +
", grade=" + grade +
'}';
}
public void introduce(){
System.out.println(toString());
}
}
Professor.java：
package com.hspedu.homework;
public class Professor extends Teacher{
public Professor(String name, int age, String post, double salary, double grade) {
super(name, age, post, salary,grade);
}
@Override
public void introduce() {
System.out.println("这是教授信息：");
super.introduce();
}
}
FProfessor.java：
package com.hspedu.homework;
public class FProfessor extends Teacher{
public FProfessor(String name, int age, String post, double salary, double grade) {
super(name, age, post, salary, grade);
}
@Override
public void introduce() {
System.out.println("这是副教授信息：");
super.introduce();
}
}
JiangShi.java：
package com.hspedu.homework;
public class JiangShi extends Teacher{
public JiangShi(String name, int age, String post, double salary, double grade) {
super(name, age, post, salary, grade);
}
@Override
public void introduce() {
System.out.println("这是讲师信息：");
super.introduce();
}
}
第四题
通过继承实现员工工资核算打印功能。
Homework04.java：
package com.hspedu.homework.homework04;
public class Homework04 {
public static void main(String[] args) {
Manager john = new Manager("John", 100, 30, 1.2);
Worker tom = new Worker("Tom", 60, 30, 1.0);
john.setBonus(1000);
john.show();
tom.show();
}
}
Employee.java：
package com.hspedu.homework.homework04;
public class Employee {
private String name;
private double salary;
private int days;
private double grade;
public Employee(String name, double salary, int days, double grade) {
this.name = name;
this.salary = salary;
this.days = days;
this.grade = grade;
}
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;
}
public int getDays() {
return days;
}
public void setDays(int days) {
this.days = days;
}
public double getGrade() {
return grade;
}
public void setGrade(double grade) {
this.grade = grade;
}
public void show(){
System.out.println(name + " 的工资为：" + salary);
}
}
Worker.java：
package com.hspedu.homework.homework04;
public class Worker extends Employee{
public Worker(String name, double salary, int days, double grade) {
super(name, salary, days, grade);
}
@Override
public void show() {
System.out.print("普通员工 ");
setSalary(getSalary() * getDays() * getGrade());
super.show();
}
}
Manager.java：
package com.hspedu.homework.homework04;
public class Manager extends Employee{
private double bonus;
public Manager(String name, double salary, int days, double grade) {
super(name, salary, days, grade);
}
public double getBonus() {
return bonus;
}
public void setBonus(double bonus) {
this.bonus = bonus;
}
@Override
public void show() {
System.out.print("经理 ");
setSalary(bonus + getSalary() * getDays() * getGrade());
super.show();
}
}
第五题
设计父类——员工类。子类：工人类，农民类，教师类，科学家类，服务生类。
Homework05.java：
package com.hspedu.homework.homework05;
public class Homework05 {
public static void main(String[] args) {
Employee[] employees = new Employee[3];
employees[0] = new Worker("张三", 3000);
employees[1] = new Farmer("小李", 2000);
employees[2] = new Waiter("丽丽", 2500);
Teacher tom = new Teacher("Tom", 5000);
Scientist liu = new Scientist("LIU", 20000);
for(int i = 0; i < 3; i++){
employees[i].setMonth(12);//设置薪资月份
employees[i].show();
}
tom.setMonth(13);//十三薪
tom.setBonus(10);//课时费
tom.setDays(100);//上了多少天课
tom.show();
liu.setMonth(15);//十五新
liu.setBonus(100000);//年终奖金
liu.show();
}
}
Employee.java：
package com.hspedu.homework.homework05;
public class Employee {
private String name;
private double salary;
private int month;
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;
}
public int getMonth() {
return month;
}
public void setMonth(int month) {
this.month = month;
}
public Employee(String name, double salary) {
this.name = name;
this.salary = salary;
}
public void show(){
System.out.println(name + " 的全年工资为：" + salary);
}
}
Worker.java：
package com.hspedu.homework.homework05;
public class Worker extends Employee{
public Worker(String name, double salary) {
super(name, salary);
}
@Override
public void show() {
System.out.print("工人 ");
setSalary(getSalary() * getMonth());
super.show();
}
}
Waiter.java：
package com.hspedu.homework.homework05;
public class Waiter extends Employee{
public Waiter(String name, double salary) {
super(name, salary);
}
@Override
public void show() {
System.out.print("服务生 ");
setSalary(getSalary() * getMonth());
super.show();
}
}
Farmer.java：
package com.hspedu.homework.homework05;
public class Farmer extends Employee{
public Farmer(String name, double salary) {
super(name, salary);
}
@Override
public void show() {
System.out.print("农民 ");
setSalary(getSalary() * getMonth());
super.show();
}
}
Teacher.java：
package com.hspedu.homework.homework05;
public class Teacher extends Employee{
private int days;
private double bonus;
public Teacher(String name, double salary) {
super(name, salary);
}
public int getDays() {
return days;
}
public void setDays(int days) {
this.days = days;
}
public double getBonus() {
return bonus;
}
public void setBonus(double bonus) {
this.bonus = bonus;
}
@Override
public void show() {
System.out.print("老师 ");
setSalary(getSalary() * getMonth() + days * bonus);
super.show();
}
}
Scientist.java：
package com.hspedu.homework.homework05;
public class Scientist extends Employee{
private double bonus;
public Scientist(String name, double salary) {
super(name, salary);
}
public double getBonus() {
return bonus;
}
public void setBonus(double bonus) {
this.bonus = bonus;
}
@Override
public void show() {
System.out.print("科学家 ");
setSalary(getSalary() * getMonth() + bonus);
super.show();
}
}
第六题
在父类和子类中通过 this 和 super 都可以调用哪些属性和方法，假定Grand、Father 和 Son 在同一个包。
class Grand{//超类
String name = "AA";
private int age = 100;
public void g1(){
}
}
class Father extends Grand{//父类
String id = "001";
private double score;
public void f1(){
//super 可以访问哪些成员（属性和方法）？super.name;super.g1();
//this 可以访问哪些成员？this.id;this.score;this.f1();this.name;this.g1();
}
}
class Son extends Father{//子类
String name = "BB";
public void g1(){
}
private void show(){
//super 可以访问哪些成员（属性和方法）？super.id;super.f1();super.name;super.g1();
//this 可以访问哪些成员？ this.name;this.g1();this.id;this.f1();
}
}
第七题
答案：
Test;Demo;Rose;Jack;
john;Jack;
第八题
扩展如下的 BankAccount 类。
class BankAccount{
private double balance;
public BankAccount(double initialBalance){
this.balance = initialBalance;
}
public void deposit(double amount){
balance += amount;
}
public void withdraw(double amount){
balance -= amount;
}
}
要求：
- 在上面类的基础上扩展，新类 CheckingAccount 对每次存款和取款都收取1美元的手续费。
- 扩展前一个练习的 BankAccount 类，新类 SavingsAccount 每个月都有利息产生 ( earnMonthlyInterest 方法被调用)，并且有每月三次免手续费的存款或取款。在 earnMonthlyInterest 方法中重置交易计数。
Homework08.java：
package com.hspedu.homework.homework08;
public class Homework08 {
public static void main(String[] args) {
// CheckingAccount checkingAccount = new CheckingAccount(1000);
// checkingAccount.deposit(10);//1000+10-1 = 1009
// checkingAccount.withdraw(10);//1009-10-1 = 998
// System.out.println(checkingAccount.getBalance());
SavingsAccount savingsAccount = new SavingsAccount(1000);
savingsAccount.deposit(100);//1000+100=1100
savingsAccount.deposit(100);//1100+100=1200
savingsAccount.deposit(100);//1200+100=1300
System.out.println(savingsAccount.getBalance());
savingsAccount.deposit(100);//1300+100-1=1399
System.out.println(savingsAccount.getBalance());
//月初，定时器自动调用一下 earnMonthlyInterest
savingsAccount.earnMonthlyInterest();//1399*1.01=1412.99
savingsAccount.deposit(100);//免手续费 1412.99+100=1512.99
System.out.println(savingsAccount.getBalance());
savingsAccount.withdraw(100);//免手续费 1512.99-100=1412.99
savingsAccount.withdraw(100);//免手续费 1412.99-100=1312.99
savingsAccount.deposit(100);//扣手续费 1312.99+100-1=1411.99
System.out.println(savingsAccount.getBalance());
}
}
BankAccount.java：
package com.hspedu.homework.homework08;
class BankAccount{
private double balance;
public BankAccount(double initialBalance){
this.balance = initialBalance;
}
public double getBalance() {
return balance;
}
public void setBalance(double balance) {
this.balance = balance;
}
public void deposit(double amount){
balance += amount;
}
public void withdraw(double amount){
balance -= amount;
}
}
CheckingAccount.java：
package com.hspedu.homework.homework08;
public class CheckingAccount extends BankAccount{
//属性
public CheckingAccount(double initialBalance) {
super(initialBalance);
}
@Override
public void deposit(double amount) {
super.deposit(amount - 1);
}
@Override
public void withdraw(double amount) {
super.withdraw(amount + 1);
}
}
SavingsAccount.java：
package com.hspedu.homework.homework08;
public class SavingsAccount extends BankAccount{
private int count = 3;
private double rate = 0.01;//利率
public SavingsAccount(double initialBalance) {
super(initialBalance);
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
public double getRate() {
return rate;
}
public void setRate(double rate) {
this.rate = rate;
}
@Override
public void deposit(double amount) {
// 判断是否可以免手续费
if(count > 0){
super.deposit(amount);
}else{
super.deposit(amount - 1);
}
count--;
}
@Override
public void withdraw(double amount) {
if(count > 0){
super.withdraw(amount);
}else{
super.withdraw(amount + 1);
}
count--;
}
public void earnMonthlyInterest(){
count = 3;//每个月我们统计上个月利息，同时将count = 3
super.deposit(getBalance() * rate);
}
}
第九题
设计一个 Point 类，其 x 和 y 坐标可以通过构造器提供。提供一个子类 LabeledPoint，其构造器接受一个标签值和 x,y 坐标，比如：new LabeledPoint(“Black Thursday",1929,230.07)，写出对应的构造器即可。
//Point类构造器
public class Point {
private double x;
private double y;
public Point(double x, double y) {
this.x = x;
this.y = y;
}
}
//LabeledPoint类构造器
public class LabeledPoint extends Point{
private String label;
public LabeledPoint(String label, double x, double y) {
super(x, y);
this.label = label;
}
}
第十题
编写 Doctor 类 {name, age,job, gender, sal} 相应的 getter() 和 setter() 方法，5个参数的构造器，重写父类的 equals()方法：public boolean equals(Obiect obj) 并判断测试类中创建的两个对象是否相等。相等就是判断属性是否相同。
Homework10.java：
package com.hspedu.homework.homework10;
public class Homework10 {
public static void main(String[] args) {
Doctor doctor = new Doctor("Tom", 18, "工人", '男', 5000);
Doctor doctor1 = new Doctor("Tom", 18, "工人", '男', 5000);
System.out.println(doctor.equals(doctor1));
}
}
Doctor.java：
package com.hspedu.homework.homework10;
public class Doctor {
private String name;
private int age;
private String job;
private char gender;
private double sal;
public Doctor(String name, int age, String job, char gender, double sal) {
this.name = name;
this.age = age;
this.job = job;
this.gender = gender;
this.sal = sal;
}
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 getJob() {
return job;
}
public void setJob(String job) {
this.job = job;
}
public char getGender() {
return gender;
}
public void setGender(char gender) {
this.gender = gender;
}
public double getSal() {
return sal;
}
public void setSal(double sal) {
this.sal = sal;
}
public boolean equals(Object obj){
if(this == obj){
return true;//判断两个对象是否相同
}
if(!(obj instanceof Doctor)){
return false;//不是Doctor类型或其子类
}
//向下转型，因为obj的运行类型是Doctor类型或其子类
Doctor doctor = (Doctor)obj;
return this.name.equals(doctor.name) && this.age == doctor.age
&& this.job.equals(doctor.job) && this.gender == doctor.gender
&& this.sal == doctor.sal;
}
}
第十一题
Homework11.java：
package com.hspedu.homework.homework11;
public class homework11 {
public static void main(String[] args) {
Person person = new Student("Tom");//向上转型
person.run();
person.eat();
Student student = (Student)person;//向下转型
student.run();
student.study();
student.eat();
}
}
Person.java：
package com.hspedu.homework.homework11;
public class Person {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Person(String name) {
this.name = name;
}
public void run(){
System.out.println("person run");
}
public void eat(){
System.out.println("person eat");
}
}
Student.java：
package com.hspedu.homework.homework11;
public class Student extends Person{
public Student(String name) {
super(name);
}
@Override
public void run() {
System.out.println("student run");
}
public void study(){
System.out.println("student study...");
}
}
第十二题
说出 == 与 equals 的区别。
第十三题
Homework13.java：
package com.hspedu.homework.homework13;
public class Homework13 {
public static void main(String[] args) {
Person[] persons = new Person[4];
persons[0] = new Student("小明", '男', 10, "00023102");
persons[1] = new Student("小红", '女', 12, "00023101");
persons[2] = new Teacher("Tom", '男', 30, 8);
persons[3] = new Teacher("Mary", '女', 35, 10);
System.out.println("==========排序前：==========");
for(int i = 0; i < persons.length; i++){
System.out.println(persons[i].toString());
new Homework13().print(persons[i]);
System.out.println(persons[i].play());
System.out.println("--------------------------");
}
new Homework13().sort(persons);
System.out.println("==========排序后：==========");
for(int i = 0; i < persons.length; i++){
System.out.println(persons[i].toString());
new Homework13().print(persons[i]);
System.out.println(persons[i].play());
System.out.println("--------------------------");
}
}
public void sort(Person[] persons){
for(int i = 0; i < persons.length - 1; i++){
for(int j = 0; j < persons.length - i - 1; j++){
if(persons[j].getAge() < persons[j + 1].getAge()){//按年龄从高到低排序
Person temp = persons[j];
persons[j] = persons[j + 1];
persons[j + 1] = temp;
}
}
}
}
public void print(Person person){
if(!(person instanceof Teacher || person instanceof Student)){
System.out.println("不是老师也不是学生");
}
if(person instanceof Student){
((Student) person).study();
}
if(person instanceof Teacher){
((Teacher) person).teach();
}
}
}
Person.java：
package com.hspedu.homework.homework13;
public class Person {
private String name;
private char sex;
private int age;
public Person(String name, char sex, int age) {
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;
}
@Override
public String toString() {
return "姓名：" + name + "\n" +
"年龄：" + sex + "\n" +
"性别：" + age + "\n";
}
public String play(){
return name + "爱玩";
}
}
Teacher.java：
package com.hspedu.homework.homework13;
public 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 toString() {
return "老师的信息：\n" + super.toString() +
"工龄：" + work_age;
}
@Override
public String play() {
return super.play() + "象棋。";
}
}
Student.java：
package com.hspedu.homework.homework13;
public 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 toString() {
return "学生的信息：\n" + super.toString() +
"学号：" + stu_id;
}
@Override
public String play() {
return super.play() + "足球。";
}
}
第十四题
答案：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；
第十五题
什么是多态，多态具体体现有哪些？(可举例说明)
举例：
package com.hspedu.homework;
public class Homework15 {
public static void main(String[] args) {
AAA obj = new BBB();//向上转型
AAA b1 = obj;
System.out.println("obj的运行类型="+ obj.getClass());//BBB
obj = new CCC();//向上转型
System.out.println("obj的运行类型="+ obj.getClass());//CCC
obj = b1;
System.out.println("obj的运行类型="+ obj.getClass());//BBB
}
}
class AAA{}
class BBB extends AAA{}
class CCC extends BBB{}
第十六题
java 的动态绑定机制是什么?
- 当调用对象的方法时，该方法会和对象的内存地址 / 运行类型绑定。
- 当调用对象的属性时，没有动态绑定机制，哪里声明，哪里使用。
