已知Main類、Person類的設計,完成Student類,Teacher類、MyTool類的設計。
函數接口定義:
class Student extends Person{ }
class Teacher extends Person{ }
class MyTool{ public static void separateStu_T(List persons,List teachers,List students){} }
Student類繼承了Person,擁有私有屬性int類型的sno和String類型的major,分別代表學號與所學專業;提供對應的set,get方法;比較方法完成按照學號比較。
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Teacher類繼承了Person,擁有私有屬性int類型的tno和String類型的subject,分別代表教師編號與所授科目;提供對應的set,get方法;比較方法完成按年齡比較。
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MyTool類中提供方法public static void separateStu_T(List persons,List teachers,List students){},方法 separateStu_T的功能是將persons線性表中的 teacher,student分別放到teachers,students兩個線性表中。
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裁判測試程序樣例:
import java.util.*;
public class Main {
public static void main(String[] args) {
List persons=getPersons(); //得到一個所有人的線性表
List teachers=new ArrayList();
List students=new ArrayList();
MyTool.separateStu_T( persons,teachers,students); //將persons線性表中的 teacher,student分別放到teachers,students兩個線性表中
Collections.sort(teachers); //對教師線性表排序
Collections.sort(students); //對學生線性表排序
showResult(teachers); //顯示教師線性表排序以後的結果
showResult(students); //顯示學生線性表排序以後的結果
}
public static List getPersons()
{
List persons=new ArrayList();
Scanner in=new Scanner(System.in);
Person person=null;
int num=Integer.parseInt(in.nextLine());
for(int i=0;i<num;i++)
{ String str=in.nextLine();
String []data=str.split(",");
if(data[0].equalsIgnoreCase("student"))
person=new Student(Integer.parseInt(data[1]),data[2],data[3],Integer.parseInt(data[4]),data[5]);
else if (data[0].equalsIgnoreCase("teacher"))
person=new Teacher(Integer.parseInt(data[1]),data[2],data[3],Integer.parseInt(data[4]),data[5]);
else person=null;
persons.add(person);
}
return persons;
}
public static void showResult(List persons)
{
for(int i=0;i<persons.size();i++)
{
Person per=(Person)persons.get(i);
System.out.println(per.getName()+","+per.getGender()+","+per.getAge());
}
}
}
abstract class Person implements Comparable
{ private String name;
private String gender;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Person(String name, String gender, int age) {
super();
this.name = name;
this.gender = gender;
this.age = age;
}
}
/* 請在這裏寫你的代碼 */
輸入樣例:
輸入的第一行是總人數n,緊跟着輸入n行,每一行代表一個人的信息。下面的例子中n=5,輸入了5個人的信息。
5
student,1001,Tom1,female,18,computer
teacher,2001,Jake1,female,35,datastructer
student,1002,Tom2,male,19,computer
student,1003,Tom3,female,20,software
teacher,2002,Jake2,female,33,database
輸出樣例:
注意:本樣例輸出結果中兩名教師是按照年齡升序排序的,三名學生是按照學號降序排序的。
Jake2,female,33
Jake1,female,35
Tom3,female,20
Tom2,male,19
Tom1,female,18
補充代碼:
class Student extends Person{
private int sno;
private String major;
public void setSno(int sno){
this.sno = sno;
}
public int getSno(){
return sno;
}
public void setMajor(String major){
this.major = major;
}
public String getMajor(){
return major;
}
public Student(int sno,String name,String gender,int age,String major){
super(name,gender,age);
this.sno = sno;
this.major = major;
}
public int compareTo(Object a){
Student o = (Student)a;
return o.sno-this.sno;
}
}
class Teacher extends Person{
private int tno;
private String subject;
Teacher(int tno,String name,String gender,int age,String subject){
super(name,gender,age);
this.tno=tno;
this.subject=subject;
}
public int getTno() {
return tno;
}
public void setTno(int tno) {
this.tno = tno;
}
public String getSubject() {
return subject;
}
public void setSubject(String subject) {
this.subject = subject;
}
public int compareTo(Object a){
Teacher o=(Teacher)a;
return this.getAge()-o.getAge();
}
}
class MyTool{
public static void separateStu_T(List persons, List teachers, List students){
for(int i = 0;i<persons.size();i++){
if(persons.get(i)instanceof Student){
students.add(persons.get(i));
}
else
teachers.add(persons.get(i));
}
}
}
感受
做這道題用了好幾個小時,其實對代碼中的很多地方都沒有了解過,比如collection.sort是幹啥的、List是什麼都不懂
此題中最重要的知識點就是compareTo()
方法的重寫以及它和sort()
的結合使用
原本,傳給sort的值如果是1或0,則升序輸出,否則降序輸出
但是在和sort結合使用的時候需要注意
這個compareTo方法是被collection.sort自動調用的(我說怎麼也找不到compareTo的調用方法,漲知識了)
而且你的輸出的內容決定了sort究竟是升序還是降序
舉個例子
(你在含age的Student類裏定義了一個compareTo方法)
降序輸出
public int compareTo(Object a){
Student stu = (Student) a;
return stu.age - this.age; //降序
}
升序輸出
public int compareTo(Object a){
Student stu = (Student) a;
return this.age - stu.age; //升序
}
不難看出,當你使用一個外來對象的屬性減-本對象的屬性時,會是降序
反之,升序