J'espère vous donner un peu de code source manuscrit.
Ma compréhension de Java est encore très superficielle. Après l'avoir écrit moi-même, je sens que je dois écrire davantage, afin de pouvoir vraiment comprendre la compréhension. J'espère que vous ne le ferez pas. tout est compris après l'avoir lu, mais faites-le vous-même, comprenez sérieusement
import java.io.*;
import java.util.Scanner;
public class StudentScoreManagementSystem {
class
Student {
//创建一个学生类
private String studentNumber;//学号
private String studentName;//姓名
private int score1;//成绩1
private int score2;//成绩2
private int totalScore;//总分
public Student() {
}
public Student(String studentNumber, String studentName, int score1, int score2, int totalScore) {
this.studentNumber = studentNumber;
this.studentName = studentName;
this.score1 = score1;
this.score2 = score2;
this.totalScore = totalScore;
}
public String getStudentName() {
return studentName;
}
public String getStudentNumber() {
return studentNumber;
}
public int getScore1() {
return score1;
}
public int getScore2() {
return score2;
}
public int getTotalScore() {
return totalScore;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
public void setStudentNumber(String studentNumber) {
this.studentNumber = studentNumber;
}
public void setScore1(int score1) {
this.score1 = score1;
}
public void setScore2(int score2) {
this.score2 = score2;
}
public void setTotalScore(int totalScore) {
this.totalScore = totalScore;
}
public String toString() {
return String.format("学号：%s\t姓名：%s\t成绩一：%d\t成绩二：%d\t总成绩：%d", studentNumber, studentName, score1, score2,
totalScore);
}
public String toString1(){
return String.format("%s,%s,%d,%d,%d", studentNumber, studentName, score1, score2,
totalScore);
}
}
class Node {
//封装学生信息节点
private Student student;
public Node next;
public Node(Student student) {
this.student = student;
this.next = null;
}
public Node(Student student, Node next) {
this.student = student;
this.next = next;
}
// public Node(String studentNumber, String studentName, int score1, int score2, int totalScore) {
// this.student.studentNumber = studentNumber;
// this.student.studentName = studentName;
// this.student.score1 = score1;
// this.student.score2 = score2;
// this.student.totalScore = totalScore;
// this.next = null;
// }
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
}
class LinkedList {
//封装保存学生信息的链表
private int size;//链表长度
private Node head;//头指针指向头结点
private Node tail;//尾指针 指向链表的最后一个结点
public LinkedList() {
size = 0;
head = tail = null;
}
public Node getHead() {
//返回头指针
return head;
}
public Node getTail() {
//返回尾指针
return tail;
}
public void setHead(Node head) {
this.head = head;
}
public void setTail(Node tail) {
this.tail = tail;
}
public boolean add(Student student) {
//向链表中添加学生信息
if (student == null)
return false;
Node n = new Node(student);
if (head == null) {
head = n;
tail = n;
} else {
tail.next = n;
tail = n;
}
this.size += 1;
return true;
}
//向链表中删除学生信息
public boolean remove(Student student) {
//删除结点 找到目标结点的前一个结点 prev.next=node.next
Node prev = null;
Node node = head;
while (node != null && !node.getStudent().getStudentNumber().equals(student.getStudentNumber())) {
//寻找目标结点
prev = node;
node = node.next;
}
if (node == null)
return false;
if (node.equals(tail)) {
tail = prev;
if (prev != null) {
prev.next = null;
}
}
Node next = node.next;
if (prev != null && next != null) {
prev.next = next;
} else if (prev != null && next == null) {
prev.next = null;
} else if (prev == null && next != null) {
head = next;
} else {
head = null;
}
this.size--;
return true;
}
//向链表中插入学生信息
public boolean insert(Student student, String studentNumber) {
//插入结点
Node dummy = new Node(null);
dummy.next = head;
Node prev = dummy;
Node curr = head;
while (curr != null && !curr.getStudent().getStudentNumber().equals(studentNumber)) {
prev = prev.next;
curr = prev.next;
}
if (curr == null)
return false;
Node newNode = new Node(student);
prev.next = newNode;
newNode.next = curr;
head = dummy.next;
size += 1;
return true;
}
}
private LinkedList studentList;
private Scanner in = new Scanner(System.in);
public StudentScoreManagementSystem() {
//全局使用的单链表 统一用这个
studentList = new LinkedList();
}
public void readStudentInfo() {
boolean repeat = false;
do {
System.out.println("*********************************************************");
Student s = new Student();
boolean correct = true;
try {
System.out.println("录入学生信息");
System.out.println("输入学生学号:");
s.setStudentNumber(in.nextLine().trim());
System.out.println("输入学生姓名:");
s.setStudentName(in.nextLine().trim());
System.out.println("输入成绩1:");
s.setScore1(Integer.parseInt(in.nextLine()));
System.out.println("输入成绩2:");
s.setScore2(Integer.parseInt(in.nextLine()));
s.setTotalScore(s.getScore1() + s.getScore2());
System.out.println(s.toString());
} catch (Exception e) {
System.out.println("非法输入");
correct = false;
}
if (correct) {
studentList.add(s);
System.out.println("录入成功...是否继续？(Y/N)");
} else {
System.out.println("录入失败...是否继续？(Y/N)");
}
if (in.nextLine().trim().equalsIgnoreCase("Y")) {
repeat = true;
} else
repeat = false;
} while (repeat);
System.out.println("*********************************************************");
System.out.println();
System.out.println();
}
public void print() {
System.out.println();
System.out.println();
System.out.println("*********************************************************");
Node curr = studentList.getHead();
while (curr != null) {
System.out.println(curr.getStudent().toString());
curr = curr.next;
}
System.out.println("*********************************************************");
System.out.println();
System.out.println();
}
//按学号查找
public void findByStudentNumber(String studentNumber) {
Node n = studentList.getHead();
while (n != null) {
if (n.getStudent().getStudentNumber().equals(studentNumber)) {
System.out.println(String.format("学号为%s的学生信息如下：", studentNumber));//%s 字符串类型 format方法的使用
System.out.println(n.getStudent().toString());//输出学生信息 如果想要实现文件里的查找 就要添加新的方法
break;
}
n = n.next;
}
if (n == null) {
System.out.println("未找到该学生信息");
}
}
//按姓名查找
public void findByStudentName(String studentName) {
Node n = studentList.getHead();
while (n != null) {
if (n.getStudent().getStudentName().equals(studentName)) {
System.out.println(n.getStudent().toString());
break;
}
n = n.next;
}
if (n == null) {
System.out.println("未找到该学生信息");
}
}
public void insertStudent() {
System.out.println();
System.out.println();
String studentNumber = null;
Student s = new Student();
boolean correct = true;
try {
System.out.println("录入学生信息");
System.out.println("输入学生学号:");
s.setStudentNumber(in.nextLine().trim());
System.out.println("输入学生姓名:");
s.setStudentName(in.nextLine().trim());
System.out.println("输入成绩1:");
s.setScore1(Integer.parseInt(in.nextLine()));
System.out.println("输入成绩2:");
s.setScore2(Integer.parseInt(in.nextLine()));
s.setTotalScore(s.getScore1() + s.getScore2());
System.out.print("输入要插入位置学生的学号：");
studentNumber = in.nextLine().trim();
} catch (Exception e) {
System.out.println("非法输入");
correct = false;
}
if (correct && studentList.insert(s, studentNumber)) {
System.out.println("插入成功");
} else {
System.out.println("插入失败");
}
System.out.println();
System.out.println();
}
public void removeStudent() {
System.out.println();
System.out.println();
System.out.print("输入要删除学生的学号：");
String studentNumber = in.nextLine().trim();
Node curr = studentList.getHead();
while (curr != null) {
if (curr.getStudent().getStudentNumber().equals(studentNumber)) {
studentList.remove(curr.getStudent());
break;
}
curr = curr.next;
}
System.out.println();
System.out.println();
}
public void find() {
//find分为按学号和姓名查找
int findType = 1;
System.out.println();
System.out.println();
System.out.println("1.按学号查找\t2.按姓名查找\t");
findType = in.nextInt();
in.nextLine();//这一步是给下面的输入做准备的
if (findType == 1) {
System.out.print("输入要查找学生学号:");
} else if (findType == 2) {
System.out.print("输入要查找学生姓名:");
}
findStudent(in.nextLine().trim(), findType);//.trim()是去掉字符串两端的空格 这里也是为什么学号要用string的原因 方便
System.out.println();
System.out.println();
}
public void findStudent(String param, int findType) {
//find的实际方法
switch (findType) {
case 1:
findByStudentNumber(param);
break;
case 2:
findByStudentName(param);
break;
}
}
public void sortStudentListByStudentNumber() {
//按学号排序
Node dummy = new Node(null);
dummy.next = null;
Node curr = studentList.getHead();
Node prev = dummy;//找到指定结点的前一个结点
while (curr != null) {
Node next = curr.next;
curr.next = null;
prev = dummy;
while (prev != null && prev.next != null
&& prev.next.getStudent().getStudentNumber().compareTo(curr.getStudent().getStudentNumber()) < 0) {
prev = prev.next;
}
curr.next = prev.next;
prev.next = curr;
studentList.setTail(curr);
curr = next;
}
studentList.setHead(dummy.next);
}
public void sortStudent() {
System.out.println();
System.out.println();
int sortType = -1;
do {
System.out.println("1.按照学号排序\t2.按照成绩一排序\t3.按照成绩二排序\t4.按照总分排序");
sortType = in.nextInt();
in.nextLine();
if (sortType < 0 || sortType > 4)
System.out.println("请输入合法序号");
sortStudentList(sortType);
} while (sortType < 0 || sortType > 4);
System.out.println();
System.out.println();
}
public void sortStudentList(int sortType) {
switch (sortType) {
case 1:
sortStudentListByStudentNumber();
break;
case 2:
sortByStudentScore1();
break;
case 3:
sortByStudentScore2();
break;
case 4:
sortByStudentTotalScore();
break;
}
}
public void sortByStudentScore1() {
Node dummy = new Node(null);
dummy.next = null;
Node curr = studentList.getHead();
Node prev = dummy;
while (curr != null) {
Node next = curr.next;
curr.next = null;
prev = dummy;
while (prev != null && prev.next != null
&& prev.next.getStudent().getScore1() < curr.getStudent().getScore1()) {
prev = prev.next;
}
curr.next = prev.next;
prev.next = curr;
studentList.setTail(curr);
curr = next;
}
studentList.setHead(dummy.next);
}
public void sortByStudentScore2() {
Node dummy = new Node(null);
dummy.next = null;
Node curr = studentList.getHead();
Node prev = dummy;
while (curr != null) {
Node next = curr.next;
curr.next = null;
prev = dummy;
while (prev != null && prev.next != null
&& prev.next.getStudent().getScore2() < curr.getStudent().getScore2()) {
prev = prev.next;
}
curr.next = prev.next;
prev.next = curr;
studentList.setTail(curr);
curr = next;
}
studentList.setHead(dummy.next);
}
public void sortByStudentTotalScore() {
Node dummy = new Node(null);
dummy.next = null;
Node curr = studentList.getHead();
Node prev = dummy;
while (curr != null) {
Node next = curr.next;
curr.next = null;
prev = dummy;
while (prev != null && prev.next != null
&& prev.next.getStudent().getTotalScore() < curr.getStudent().getTotalScore()) {
prev = prev.next;
}
curr.next = prev.next;
prev.next = curr;
studentList.setTail(curr);
curr = next;
}
studentList.setHead(dummy.next);
}
public void summary() {
int summaryType = -1;
do {
System.out.println();
System.out.println();
System.out.println("1.统计成绩一平均分\t2.统计成绩二平均分\t3.统计总成绩平均分");
summaryType = in.nextInt();
in.nextLine();
if (summaryType < 1 || summaryType > 3)
System.out.println("输入合法序号");
} while (summaryType < 1 || summaryType > 3);
switch (summaryType) {
case 1:
showAverageScore1();
break;
case 2:
showAverageScore2();
break;
case 3:
showAverageTotalScore();
break;
}
}
public void showAverageScore2() {
System.out.println();
System.out.println();
Node curr = studentList.getHead();
int sum = 0;
int count = 0;
while (curr != null) {
count += 1;
sum += curr.getStudent().getScore2();
System.out
.print(String.format("%s:%d\t", curr.getStudent().getStudentName(), curr.getStudent().getScore2()));
if (count % 5 == 0)
System.out.println();
curr = curr.next;
}
System.out.println();
System.out.println(String.format("科目二的平均成绩为：%.3f", sum / (count * 1.0)));
System.out.println();
System.out.println();
}
public void showAverageTotalScore() {
System.out.println();
System.out.println();
Node curr = studentList.getHead();
int sum = 0;
int count = 0;
while (curr != null) {
count += 1;
sum += curr.getStudent().getTotalScore();
System.out.print(
String.format("%s:%d\t", curr.getStudent().getStudentName(), curr.getStudent().getTotalScore()));
if (count % 5 == 0)
System.out.println();
curr = curr.next;
}
System.out.println();
System.out.println(String.format("总成绩的平均值为：%.3f", sum / (count * 1.0)));
System.out.println();
System.out.println();
}
public void showAverageScore1() {
System.out.println();
System.out.println();
Node curr = studentList.getHead();
int sum = 0;
int count = 0;
while (curr != null) {
count += 1;
sum += curr.getStudent().getScore1();
System.out
.print(String.format("%s:%d\t", curr.getStudent().getStudentName(), curr.getStudent().getScore1()));
if (count % 5 == 0)
System.out.println();
curr = curr.next;
}
System.out.println();
System.out.println(String.format("科目一的平均成绩为：%.3f", sum / (count * 1.0)));
System.out.println();
System.out.println();
}
public void welcome() {
System.out.println("*********************************************************");
System.out.println("* 欢迎使用学生成绩管理系统 *");
System.out.println("* 1.录入学生信息 2.打印学生信息 3.插入学生信息 *");
System.out.println("* 4.查找学生信息 5.删除学生信息 6.排序学生信息 *");
System.out.println("* 7.分类统计 8.保存到文件中 9.退出系统 *");
System.out.println("*********************************************************");
}
//保存方法 但是这个方法有一个bug 就是在程序重启后再次写入时还是会覆盖 如何去改变
// 最后发现bug出现在fileoutstream流这里 当我把这个注释掉之后 就可以正常追加而不会覆盖，我觉得是因为它创建了新的student.txt文件
public void save() throws IOException{
File f = new File("student.txt");
// FileOutputStream fop = new FileOutputStream(f); 这个是字节流
// 构建FileOutputStream对象,文件不存在会自动新建 应该就是这个东西会创建新的
FileWriter writer = new FileWriter(f);
// 如果加 true表示在writer对文件再次写入时，会在该文件的结尾续写，并不会覆盖掉。
//为了配合load，变成每次重新的覆盖写入
//FileWriter是字符流
Node p = studentList.getHead();
while (p != null) {
writer.append(p.getStudent().toString1()); // 写入到缓冲区
writer.append("\r" + "\n");// 换行
p = p.next;
}
writer.close();
// 关闭写入流,同时会把缓冲区内容写入文件,所以上面的注释掉
// fop.close();
// // 关闭输出流,释放系统资源
System.out.println("保存成功");
}
//读取方法 在程序一开始时就默认读取 这样就保证了
public void load() throws IOException {
// 需要做的一个内容就是把string的内容变成student类并添加到链表中
String filepath = "student.txt";
BufferedReader reader = new BufferedReader(new FileReader(filepath));
String temp = reader.readLine();
while (temp != null) {
// 解析字符串
String[] data = temp.split(",");//这个很重要
String studentNumber=data[0];
String studentName=data[1];
int score1 = Integer.parseInt(data[2]); //用Double.parseDouble()是把括号里面内容变成double类型的。 如果要变成int,则用Integer.parseInt()
int score2 = Integer.parseInt(data[3]);
int totalScore = Integer.parseInt(data[4]);
studentList.add(new Student(studentNumber, studentName, score1,score2,totalScore));
temp = reader.readLine();
}
reader.close();
}
// 结束方法
public void out(){
System.exit(0);
}
public void main() throws IOException {
int choice = 0;
load();
while (true) {
welcome();
do {
System.out.print("请选择:");
choice = Integer.parseInt(in.nextLine().trim());
if (choice < 1 || choice > 10)
System.out.println("请输入合法序号!");
} while (choice < 1 || choice > 10);
switch (choice) {
case 1:
readStudentInfo();
break;
case 2:
print();
break;
case 3:
insertStudent();
break;
case 4:
find();
break;
case 5:
removeStudent();
break;
case 6:
sortStudent();
break;
case 7:
summary();
break;
case 8:
save();
break;
case 9:
out();
break;
}
}
}
public static void main(String[] args) throws Exception {
StudentScoreManagementSystem SSMS = new StudentScoreManagementSystem();
SSMS.main();
}
}