南邮-JAVA实验课（三）
第三次实验
本次实验主要练习知识点是：
类的继承和派生的概念
super关键词的使用
父类对象和子类对象之间的赋值关系
多态的实现
抽象类和抽象方法的定义和使用
接口的定义和使用
异常的定义和使用
1、类的继承
在前面实验二已定义的学生类Student的基础上，以Student类为父类，为学生类派生出一个子类为大学生类（CollegeStudent）。CollegeStudent 类在学生类上增加一个专业（profession）数据属性；方法上增加获得专业和设置专业两个方法。并对超类中的toString( )方法进行重写，使得CollegeStudent类中的toString( )方法除了显示学生类的信息外，还要显示它的专业属性。编写测试程序的主类。在主类中创建一个Student对象和CollegeStudent对象，并显示或修改这两个对象的属性值。
package javalab.student;
public class Student {
protected String StuNub,ClassNub,Name,Sex;
protected int Age;
public static int count = 0;
public Student(String StuNub,String ClassNub,String Name,String Sex,int Age){
this.StuNub = StuNub;
this.ClassNub = ClassNub;
this.Name = Name;
this.Sex = Sex;
this.Age = Age;
count++;
}
public String get_StuNub() {
return StuNub;
}
public String get_ClassNub() {
return ClassNub;
}
public String get_Name() {
return Name;
}
public String get_Sex() {
return Sex;
}
public int get_Age() {
return Age;
}
public void set_StuNub(String StuNub) {
this.StuNub = StuNub;
}
public void set_ClassNub(String ClassNub) {
this.ClassNub = ClassNub;
}
public void set_Name(String Name) {
this.Name = Name;
}
public void set_Sex(String Sex) {
this.Sex = Sex;
}
public void set_Age(int Age) {
this.Age = Age;
}
public static int get_count() {
return count;
}
public String toString() {
String s = "学号："+StuNub +"，班级：" + ClassNub + "，姓名：" + Name + "，性别：" + Sex + "，年龄：" + Age ;
return s;
}
}
package javalab;
import javalab.student.Student;
public class Main {
public static void main(String args[]) {
Student std1 = new Student("B16031114", "B160311", "李常委", "男", 21);
CollegeStudent std2 = new CollegeStudent("B16031188", "B160311", "李伟", "男", 22, "光电子学");
System.out.println("Student对象:\n"+std1.toString());
System.out.println("CollegeStudent对象:\n"+std2.toString());
std1.set_Age(22);
std2.setProfession("光电信息科学与工程");
System.out.println("信息修改以后为：");
System.out.println("Student对象:\n"+std1.toString());
System.out.println("CollegeStudent对象:\n"+std2.toString());
}
}
class CollegeStudent extends Student{
private String profession;
public CollegeStudent(String StuNub, String ClassNub, String Name, String Sex, int Age, String profession) {
super(StuNub, ClassNub, Name, Sex, Age);
this.profession = profession;
}
public void setProfession(String profession) {
this.profession = profession;
}
public String getProfession() {
return this.profession;
}
public String toString () {
return "学号："+StuNub +"，班级：" + ClassNub + "，姓名：" + Name + "，性别：" + Sex + "，年龄：" + Age +"，专业：" + profession;
}
}
2、继承和多态
设计一个人员类（Person），其中包含一个方法pay，代表人员的工资支出。再从Person类派生出助教类（Assistant）、讲师类（Instructor）、副教授类（Assistant Professor）和教授类（Professor）。其中：工资支出=基本工资+授课时数*每课时兼课金。
但助教基本工资为800，每课时兼课金25，讲师基本工资为1000，每课时兼课金35，
副教授基本工资为1200，每课时兼课金40，教授基本工资为1400，每课时兼课金50。
① 将Person定义为抽象类，pay为抽象方法，设计程序实现多态性。
② 将Person定义为接口，设计程序实现多态性。
Person定义为普通类：
public class Main {
public static void main(String args[]) {
Assistant assistant = new Assistant(10);
Instructor instructor = new Instructor(10);
Assistant_Professor assistant_professor = new Assistant_Professor(10);
Professor professor = new Professor(10);
System.out.println("助教工资支出：" + assistant.pay());
System.out.println("讲师工资支出：" + instructor.pay());
System.out.println("副教授工资支出：" + assistant_professor.pay());
System.out.println("教授工资支出：" + professor.pay());
}
}
class Person{
protected int payload, base_pay, teaching_hours, class_pay;
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
};
}
class Assistant extends Person{
public Assistant(int teaching_hours) {
base_pay = 800;
class_pay = 25;
this.teaching_hours = teaching_hours;
}
}
class Instructor extends Person{
public Instructor(int teaching_hours) {
base_pay = 1000;
class_pay = 35;
this.teaching_hours = teaching_hours;
}
}
class Assistant_Professor extends Person{
public Assistant_Professor(int teaching_hours) {
base_pay = 1200;
class_pay = 40;
this.teaching_hours = teaching_hours;
}
}
class Professor extends Person{
public Professor(int teaching_hours) {
base_pay = 1400;
class_pay = 50;
this.teaching_hours = teaching_hours;
}
}
Person定义为抽象类：
public class Main {
public static void main(String args[]) {
Assistant assistant = new Assistant(10);
Instructor instructor = new Instructor(10);
Assistant_Professor assistant_professor = new Assistant_Professor(10);
Professor professor = new Professor(10);
System.out.println("助教工资支出：" + assistant.pay());
System.out.println("讲师工资支出：" + instructor.pay());
System.out.println("副教授工资支出：" + assistant_professor.pay());
System.out.println("教授工资支出：" + professor.pay());
}
}
abstract class Person{
abstract public int pay();
}
class Assistant extends Person{
private int payload, base_pay, teaching_hours, class_pay;
public Assistant(int teaching_hours) {
base_pay = 800;
class_pay = 25;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
class Instructor extends Person{
private int payload, base_pay, teaching_hours, class_pay;
public Instructor(int teaching_hours) {
base_pay = 1000;
class_pay = 35;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
class Assistant_Professor extends Person{
private int payload, base_pay, teaching_hours, class_pay;
public Assistant_Professor(int teaching_hours) {
base_pay = 1200;
class_pay = 40;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
class Professor extends Person{
private int payload, base_pay, teaching_hours, class_pay;
public Professor(int teaching_hours) {
base_pay = 1400;
class_pay = 50;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
Person定义为接口：
public class Main {
public static void main(String args[]) {
Assistant assistant = new Assistant(10);
Instructor instructor = new Instructor(10);
Assistant_Professor assistant_professor = new Assistant_Professor(10);
Professor professor = new Professor(10);
System.out.println("助教工资支出：" + assistant.pay());
System.out.println("讲师工资支出：" + instructor.pay());
System.out.println("副教授工资支出：" + assistant_professor.pay());
System.out.println("教授工资支出：" + professor.pay());
}
}
interface Person{
abstract public int pay();
}
class Assistant implements Person{
private int payload, base_pay, teaching_hours, class_pay;
public Assistant(int teaching_hours) {
base_pay = 800;
class_pay = 25;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
class Instructor implements Person{
private int payload, base_pay, teaching_hours, class_pay;
public Instructor(int teaching_hours) {
base_pay = 1000;
class_pay = 35;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
class Assistant_Professor implements Person{
private int payload, base_pay, teaching_hours, class_pay;
public Assistant_Professor(int teaching_hours) {
base_pay = 1200;
class_pay = 40;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
class Professor implements Person{
private int payload, base_pay, teaching_hours, class_pay;
public Professor(int teaching_hours) {
base_pay = 1400;
class_pay = 50;
this.teaching_hours = teaching_hours;
}
public int pay() {
payload = base_pay + teaching_hours*class_pay;
return payload;
}
}
- 在课堂上老师强调了多态，0-0，多态我没使用哇！！！！！
- 以上代码的主方法内的程序段替换一下就好啦！
源代码的主方法：
public static void main(String args[]) {
Assistant assistant = new Assistant(10);
Instructor instructor = new Instructor(10);
Assistant_Professor assistant_professor = new Assistant_Professor(10);
Professor professor = new Professor(10);
System.out.println("助教工资支出：" + assistant.pay());
System.out.println("讲师工资支出：" + instructor.pay());
System.out.println("副教授工资支出：" + assistant_professor.pay());
System.out.println("教授工资支出：" + professor.pay());
}
替换为：
public static void main(String args[]) {
Person person;
person = new Assistant(10);
System.out.println("助教工资支出：" + person.pay());
person = new Instructor(10);
System.out.println("讲师工资支出：" + person.pay());
person = new Assistant_Professor(10);
System.out.println("副教授工资支出：" + person.pay());
person = new Professor(10);
System.out.println("教授工资支出：" + person.pay()); }
}
3、异常的定义和使用
从键盘输入两个数，进行相除，显示商。当输入串中含有非数字时或除数为0时，通过异常处理机制，使程序能正确运行。
import java.util.Scanner;
public class Main {
public static void chufa(String a, String b) throws StrZeroNumException{
int chushu = 0, beichushu = 0;
boolean sflag = false,zflag = false;
try{
beichushu = Integer.parseInt(a);
chushu = Integer.parseInt(b);
}catch(Exception e){
sflag = true;
StrZeroNumException ze = new StrZeroNumException();
throw ze;
}
if(chushu == 0) {
zflag = true;
StrZeroNumException ze = new StrZeroNumException(chushu);
throw ze;
}
if((!zflag)&&(!sflag)) {
System.out.println(beichushu+"/" + chushu + "=" + beichushu/chushu);
}
}
public static void main(String args[]) {
String a,b;
Scanner s = new Scanner(System.in);
a = s.next();
b = s.next();
try {
chufa(a, b);
}catch(StrZeroNumException ze){
System.out.println(ze.toString());
}
}
}
class StrZeroNumException extends Exception{
String message;
public StrZeroNumException(int a) {
message = "除数不能为0";
}
public StrZeroNumException() {
message = "输入串中含有非数字";
}
public String toString(){
return message;
}
}
- 需要学习异常的定义的用以上方法verygood
- 其实我们可以直接使用已有的异常来捕获它们，经测试代码如下：
import java.util.InputMismatchException;
import java.util.Scanner;
public class Main {
public static void main(String args[]){
int a = 0,b = 0;
Scanner s = new Scanner(System.in);
try{
a = s.nextInt();
b = s.nextInt();
s.close();
a = a/b;
}catch(InputMismatchException e){
System.out.println("输入的有非数字类型！");
}catch (ArithmeticException e) {
System.out.println("除数为0！");
}
}
}
- 实验目录：
- 南邮-JAVA实验课（一）
- 南邮-JAVA实验课（二）
- 南邮-JAVA实验课（三）
- 南邮-JAVA实验课（四）