嘿，我的 randomAccessFile 应用程序没有将学生添加到文件中。我已经使用 arrayList 设置了一个学生商店，并且添加的学生正在添加到商店中，但它没有显示在文件“ContactDetails.txt”中。谁能看出出了什么问题吗？
这是我的代码: 主应用程序
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Scanner;
public class MainApp
{
//---------------------------------------------------------------------------------------
// The Scanner is declared here for use throughout the whole MainApp.
//---------------------------------------------------------------------------------------
private static Scanner keyboard = new Scanner(System.in);
public static void main(String[] args) throws Exception
{
new MainApp().start();
}
public void start()throws Exception
{
StudentStore details = new StudentStore();
Student a = new Student("Becky O'Brien", "DKIT26", "0876126944", "bexo@hotmail.com");
Student b = new Student("Fabio Borini", "DKIT28", "0876136944", "fabioborini@gmail.com");
Student c = new Student("Gaston Ramirez", "DKIT29", "0419834501", "gramirez@webmail.com");
Student d = new Student("Luis Suarez", "DKIT7", "0868989878", "luissuarez@yahoo.com");
Student e = new Student("Andy Carroll", "DKIT9", "0853456788", "carroll123@hotmail.com");
details.add(a);
details.add(b);
details.add(c);
details.add(d);
details.add(e);
//details.print();
RandomAccessFile file = new RandomAccessFile("ContactDetails.txt","rw");
//getBytes() returns an array of bytes.
//Because i have put the store in a static Array.(I done this because i could find no other
//Simple way to write a Student Object.)
//None of the methods of the RandomAccessFile write class worked with this.
//Student[] students = {a,b,c,d,e};
details.write(file);
//details.readAll(file);
int choice;
System.out.println("Welcome to the Company Database.");
do
{
choice = MenuMethods.getMenuChoice( "1.\tView" +
"\n2.\tAdd"+
"\n3.\tDelete" +
"\n4.\tDelete All " +
"\n5.\tEdit"+
"\n6.\tSearch" +
"\n7.\tStore" +
"\n8.\tExit", 8,
"Please enter your choice:", "Error [1,8] Only");
// String temp = keyboard.nextLine(); This prevented entering the choice.
//---------------------------------------------------------------------------------------
// Name: Switch Statement.
// Description: This is used for a menu system.
//---------------------------------------------------------------------------------------
switch (choice)
{
//---------------------------------------------------------------------------------------
// Name: Case 1: View All
// Description: Choice 1 is to view all employee's in the store.
//---------------------------------------------------------------------------------------
case 1:
System.out.println("View All");
details.readAll(file);
break;
//---------------------------------------------------------------------------------------
// Name: Case 2: Add
// Description: Choice 2 is to add an employee to the store.
//---------------------------------------------------------------------------------------
case 2:
System.out.println("Add");
Student student = MenuMethods.userInput();
details.add(student);
break;
//---------------------------------------------------------------------------------------
// Name: Case 3: Delete by Name.
// Description: Choice 3 gives the user an option to delete an employee by name.
//---------------------------------------------------------------------------------------
case 3:
System.out.println("Delete by Name.");
//Employee employeeDelete = MenuMethods.userInputByName();
//Store.searchByName(employeeDelete.getEmployeeName());
//Store.remove(employeeDelete.getEmployeeName());
break;
//---------------------------------------------------------------------------------------
// Name: Case 4: Delete All.
// Description: Choice 4 gives the user a choice to delete all employee's in the store.
//---------------------------------------------------------------------------------------
case 4:
System.out.println("Delete All.");
//Store.clear();
break;
//---------------------------------------------------------------------------------------
// Name: Case 4: Edit.
// Description: Choice 4 gives the user an option to edit the employee's in the store.
// This consists of changing the employee's name,id and e-mail address.
//---------------------------------------------------------------------------------------
case 5:
System.out.println("Edit");
break;
//---------------------------------------------------------------------------------------
// Name: Case 6: Search.
// Description: Choice 6 gives the user 2 options: Search by name and Search by email.
// Search will run through the store and output the employee match the user inputs.
//---------------------------------------------------------------------------------------
case 6:
break;
//---------------------------------------------------------------------------------------
// Name: Case 7: Store.
// Description: Choice 7 gives the user an option to copy and read a store
// using read and write class from Java.
//---------------------------------------------------------------------------------------
case 7:
break;
//---------------------------------------------------------------------------------------
// Name: Case 8: Exit.
// Description: Choice 8 will exit the application.
//---------------------------------------------------------------------------------------
case 8:
System.out.println("Exit");
break;
}
} while (choice != 8);
file.close();
}
}
学生商店
//---------------------------------------------------------------------------
//Imports.
//---------------------------------------------------------------------------
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.List;
//---------------------------------------------------------------------------
public class StudentStore
{
//---------------------------------------------------------------------------
//ArrayList declaration.
//---------------------------------------------------------------------------
List<Student> students = new ArrayList<Student>();
//---------------------------------------------------------------------------
//Name: Add method.
//Description: Adds a student to the ArrayList.
//---------------------------------------------------------------------------
public void add(Student student)
{
students.add(student);
}
//---------------------------------------------------------------------------
//Name: DeleteAll method.
//Description: Delete's everything in the ArrayList.
//---------------------------------------------------------------------------
public void deleteAll()
{
students.clear();
}
//---------------------------------------------------------------------------
//Name: Print method.
//Description: Prints out the contents of the ArrayList.
//---------------------------------------------------------------------------
public void print()
{
for (int i = 0; i < students.size(); i++)
{
Student a = students.get(i);
System.out.println(a.toString());
}
}
public int size()
{
return (students == null) ? 0 : students.size();
}
public void write(RandomAccessFile file) throws IOException
{
for (Student s: students)
{
byte[] bytes = s.toString().getBytes();
for(byte byteWrite : bytes)
{
file.writeByte(byteWrite);
}
}
}
public void readAll(RandomAccessFile file) throws IOException
{
final int Record_Length = 30;
int recordNumber = 0;
file.seek((recordNumber) * Record_Length);
String code ="";
for(int i = 0; i < 30; i++)
{
code += file.readLine() + "\n";
}
System.out.println(code);
}
}
菜单方法
//---------------------------------------------------------------------------------------
// Name: Imports.
// Description: To allow the use of different Java classes.
//---------------------------------------------------------------------------------------
import java.util.Scanner;
//---------------------------------------------------------------------------------------
public class MenuMethods
{
private static Scanner keyboard = new Scanner(System.in);
//---------------------------------------------------------------------------------------
// Methods for the Company Application menu.
//---------------------------------------------------------------------------------------
//---------------------------------------------------------------------------------------
// Name: getMenuChoice.
// Description: Method for validating the choice.
//---------------------------------------------------------------------------------------
public static int getMenuChoice(String menuString, int limit,String prompt, String errorMessage)
{
System.out.println(menuString);
int choice = inputAndValidateInt(1, limit, prompt, errorMessage);
return choice;
}
//---------------------------------------------------------------------------------------
// Name: inputAndValidateInt.
// Description: This method is used in the getMenuChoice method.
//---------------------------------------------------------------------------------------
public static int inputAndValidateInt(int min, int max, String prompt,String errorMessage)
{
int number;
boolean valid;
do
{
System.out.print(prompt);
number = keyboard.nextInt();
valid = number <= max && number >= min;
if (!valid)
{
System.out.println(errorMessage);
}
} while (!valid);
return number;
}
//---------------------------------------------------------------------------------------
// Name: userInput
// Description: This method is used in the MainApp to give the user capability to enter
// the details when adding details of an employee into the store.
//---------------------------------------------------------------------------------------
public static Student userInput()
{
String temp = keyboard.nextLine();
Student s = null;
System.out.println("Please enter the Student Name:");
String studentName = keyboard.nextLine();
System.out.println("Please enter the Student ID:");
String studentId = keyboard.nextLine();
System.out.println("Please enter the Student E-mail address:");
String studentEmail = keyboard.nextLine();
System.out.println("Please enter the Student telephone number:");
String studentTelephoneNumber = keyboard.nextLine();
return s = new Student(studentName, studentId, studentEmail,studentTelephoneNumber);
}
//---------------------------------------------------------------------------------------
// Name: userInputByName.
// Description: This method is used in the MainApp to give the user capability to search by name.
//---------------------------------------------------------------------------------------
public static Student userInputByName()
{
// String temp is for some reason needed. If it is not included
// The code will not execute properly.
String temp = keyboard.nextLine();
Student s = null;
System.out.println("Please enter the Student Name:");
String studentName = keyboard.nextLine();
return s = new Student(studentName);
}
//---------------------------------------------------------------------------------------
// Name: userInputByEmail
// Description: This method is used in the MainApp to give the user capability to search by email.
//---------------------------------------------------------------------------------------
public static String userInputByEmail()
{
// String temp is for some reason needed. If it is not included
// The code will not execute properly.
String temp = keyboard.nextLine();
Student s = null;
System.out.println("Please enter the StudentEmail:");
String studentEmail = keyboard.nextLine();
// This can use the employeeName's constructor because java accepts the
// parameters instead
// of the name's.
return studentEmail;
}
//---------------------------------------------------------------------------------------
}
学生
import java.io.Serializable;
public class Student implements Serializable
{
//---------------------------------------------------------------------------
// Class Variables.
//---------------------------------------------------------------------------
private String studentName;
private String studentId;
private String studentTelephoneNumber;
private String studentEmail;
//---------------------------------------------------------------------------
// Constructor.
//---------------------------------------------------------------------------
public Student(String studentName, String studentId,String studentTelephoneNumber, String studentEmail)
{
this.studentName = studentName;
this.studentId = studentId;
this.studentTelephoneNumber = studentTelephoneNumber;
this.studentEmail = studentEmail;
}
//---------------------------------------------------------------------------------------
// Overloading the constructor for the use with userInputByName method.
//---------------------------------------------------------------------------------------
public Student(String studentName)
{
this.studentName = studentName;
}
//---------------------------------------------------------------------------
// Getters.
//---------------------------------------------------------------------------
public String getStudentName()
{
return studentName;
}
public String getStudentId()
{
return studentId;
}
public String getStudentTelephoneNumber()
{
return studentTelephoneNumber;
}
public String getStudentEmail()
{
return studentEmail;
}
//---------------------------------------------------------------------------
// Setters.
//---------------------------------------------------------------------------
public void setStudentName(String studentName)
{
this.studentName = studentName;
}
public void setStudentId(String studentId)
{
this.studentId = studentId;
}
public void setStudentTelephoneNumber(String studentTelephoneNumber)
{
this.studentTelephoneNumber = studentTelephoneNumber;
}
public void setStudentEmail(String studentEmail)
{
this.studentEmail = studentEmail;
}
//---------------------------------------------------------------------------
// toString.
//---------------------------------------------------------------------------
public String toString()
{
return "---------------------------Student--------------------------- " +
"\nStudent Name:" + studentName +
"\nStudent Id:"+ studentId +
"\nStudent Telephone Number:"+ studentTelephoneNumber +
"\nStudent Email:" + studentEmail +"\n\n";
}
}
最佳答案
请发布学生类(class)代码 是否重写 Student 类中的 toString() 方法
我测试了你的代码，如果我输入1，它将打印你在主方法中输入的所有学生信息。 但是如果我输入2，输入学生信息后，你的代码只是将Arraylist中的信息添加到内存中，而不是将其输出到文件中。那么我输入1，它不会输出我之前输入的新学生信息。
我认为您可能需要输出新的学生信息以归档。
编辑
case 2:
System.out.println("Add");
Student student = MenuMethods.userInput();
details.add(student);
break;
至
case 2:
System.out.println("Add");
Student student = MenuMethods.userInput();
details.add(student);
file.write(student.toString().getBytes());
break;
以及更多您刚刚在 read All 方法中读取了文件的前 30 行 改变
public void readAll(RandomAccessFile file) throws IOException
{
final int Record_Length = 30;
int recordNumber = 0;
file.seek((recordNumber) * Record_Length);
String code ="";
for(int i = 0; i < 30; i++)
{
code += file.readLine() + "\n";
}
System.out.println(code);
}
至
public void readAll(RandomAccessFile file) throws IOException
{
file.seek(0);
String code;
while((code=file.readLine())!=null)
System.out.println(code);
}
关于java - 添加方法不在 RandomAccessFile 中添加 Student，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11903004/