学生信息管理系统V0.3（优化文件存取、增加修改删除功能）

0.3版更新内容：
1.程序启动时从文件中加载学生信息到HashMap中；
2.所有操作都在内存中进行，操作完成后写入文件；
3.增加修改、删除功能。

Student.java：学生类

package cn.edu.ahau.mgc.stu;

public class Student {

private String id;
private String name;
private int age;

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

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;
}
}

StudentAction.java：学生信息处理类

package cn.edu.ahau.mgc.stu;

import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class StudentAction {

Scanner sc = new Scanner(System.in);
private HashMap<String, Student> stus;

public void init() {
try {
this.stus = DAOFactory.getStudentDAOInstance().load();
} catch (Exception e) {
System.out.println("信息初始化失败！");
}
}

public void add(Student stu) {
this.stus.put(stu.getId(), stu);
try {
DAOFactory.getStudentDAOInstance().save(stus);
} catch (Exception e) {
System.out.println("学生信息保存失败！");
}
}

public void showAll() {
Iterator<Student> iter = this.stus.values().iterator();
this.printHeader();
while (iter.hasNext()) {
Student stu = iter.next();
this.print(stu);
}
this.printFooter();
}

public void printHeader() {
System.out.println("------------------------");
System.out.println("学号/t姓名/t年龄");
System.out.println("------------------------");
}

public void printFooter() {
System.out.println("------------------------");
}

public void print(Student stu) {
System.out.println(stu.getId() + "/t" + stu.getName() + "/t" + stu.getAge());
}

public Student queryById(String id) {
Student stu = null;
if (stus.containsKey(id)) {
stu = this.stus.get(id);
}
if (stu != null) {
this.printHeader();
this.print(stu);
this.printFooter();
} else {
System.out.println("对不起，没找到您要查找的学生！");
}
return stu;
}

public void delete(String id) {
stus.remove(id);
try {
DAOFactory.getStudentDAOInstance().save(stus);
} catch (Exception e) {
System.out.println("学生信息保存失败！");
}
}

public void modify(Student stu) {
stus.put(stu.getId(), stu);
try {
DAOFactory.getStudentDAOInstance().save(stus);
} catch (Exception e) {
System.out.println("学生信息保存失败！");
}
}
}

DAOFactory.java：数据操作工厂类

package cn.edu.ahau.mgc.stu;

public class DAOFactory {

public static StudentDAO getStudentDAOInstance() {
return new StudentDAOImpl();

}
}

StudentDAO.java：学生信息数据操作接口

package cn.edu.ahau.mgc.stu;

import java.util.HashMap;

public interface StudentDAO {

//从文件中读取学生信息
public HashMap<String, Student> load() throws Exception;
//将学生信息写入文件
public void save(HashMap<String, Student> stus) throws Exception;
}

StudentDAOImpl.java：学生信息数据操作实现类

package cn.edu.ahau.mgc.stu;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Iterator;

public class StudentDAOImpl implements StudentDAO {

public static final String FILE_PATH = "DB/student.txt";

public HashMap<String, Student> load() throws Exception {
HashMap<String, Student> stus = new HashMap<String, Student>();
FileReader fr = null;
BufferedReader br = null;
try {
fr = new FileReader(FILE_PATH);
br = new BufferedReader(fr);
String stuStr = null;
while ((stuStr = br.readLine()) != null) {
String[] stuMsg = stuStr.split(":");
if (stuMsg.length == 3) {
Student stu = new Student();
stu.setId(stuMsg[0]);
stu.setName(stuMsg[1]);
int age = 20;
try {
age = Integer.parseInt(stuMsg[2]);
} catch (NumberFormatException e) {
age = 20;
}
stu.setAge(age);
stus.put(stuMsg[0], stu);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
throw new Exception(e);
} catch (IOException e) {
e.printStackTrace();
throw new Exception(e);
} finally {
if (br != null) {
try {
br.close();
} catch (Exception e) {
e.printStackTrace();
throw new Exception(e);
}
br = null;
}
if (fr != null) {
try {
fr.close();
} catch (Exception e) {
e.printStackTrace();
throw new Exception(e);
}
fr = null;
}
}
return stus;
}

public void save(HashMap<String, Student> stus) throws Exception {
FileWriter fw = null;
PrintWriter pw = null;
try {
fw = new FileWriter(FILE_PATH);
pw = new PrintWriter(fw, true);
for (Iterator iterator = stus.values().iterator(); iterator.hasNext();) {
Student stu = (Student) iterator.next();
pw.println(stu.getId() + ":" + stu.getName() + ":" + stu.getAge());
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (pw != null) {
pw.close();
pw = null;
}
if (fw != null) {
try {
fw.close();
} catch (IOException e) {
e.printStackTrace();
throw new Exception(e);
}
fw = null;
}
}
}

}

StudentMgr.java：学生信息管理类

package cn.edu.ahau.mgc.stu;

import java.util.Scanner;

public class StudentMgr {

public static void main(String[] args) {
StudentAction sa = new StudentAction();
Scanner sc = new Scanner(System.in);
boolean flag = true;
while (flag) {
sa.init();
showMenu();
int selected = sc.nextInt();
switch(selected) {
case 1 :
add(sa, sc);
break;
case 2 :
sa.showAll();
break;
case 3 :
query(sa, sc);
break;
case 4 :
delete(sa, sc);
break;
case 5 :
modify(sa, sc);
break;
case 6 :
flag = false;
break;
}
}
}

private static void modify(StudentAction sa, Scanner sc) {
System.out.println("请输入要修改的学生学号：");
String id = sc.next();
System.out.println("请重新输入该学生姓名：");
String name = sc.next();
System.out.println("请重新输入该学生年龄：");
int age = sc.nextInt();
Student stu = new Student();
stu.setId(id);
stu.setName(name);
stu.setAge(age);
sa.modify(stu);
}

private static void delete(StudentAction sa, Scanner sc) {
System.out.println("请输入要删除的学生学号：");
String id = sc.next();
sa.delete(id);

}

private static void query(StudentAction sa, Scanner sc) {
System.out.println("请输入学号：");
String id = sc.next();
sa.queryById(id);

}

private static void add(StudentAction sa, Scanner sc) {
Student stu = new Student();
System.out.println("请输入学生学号：");
String id = sc.next();
System.out.println("请输入学生姓名：");
String name = sc.next();
System.out.println("请输入学生年龄：");
int age = sc.nextInt();
stu.setId(id);
stu.setName(name);
stu.setAge(age);
sa.add(stu);

}

private static void showMenu() {
System.out.println("学生信息管理菜单：");
System.out.println("（1）增加学生信息");
System.out.println("（2）显示所有学生信息");
System.out.println("（3）根据学号查询学生信息");
System.out.println("（4）删除学生信息");
System.out.println("（5）修改学生信息");
System.out.println("（6）退出管理");
}

}

student.txt：学生数据文件

1001:Magci:20
1002:MGC:20
1003:haha:24
1005:lala:19
1004:test:23