[英]How to save and load an array list of objects?
I have a class Employees that has methods add, delete, display and search employees in an array list.我有一个员工类,它具有在数组列表中添加、删除、显示和搜索员工的方法。 Now I'm trying to create a file handler to save and read this data but for some reason it isn't working and it isn't creating a file or reading it.
现在我正在尝试创建一个文件处理程序来保存和读取这些数据,但由于某种原因它不起作用,它没有创建文件或读取它。 Can anyone find a problem with my code please?
任何人都可以找到我的代码的问题吗?
I tested your code but couldn't find any problem.我测试了你的代码,但没有发现任何问题。
why don't you try to catch Throwable and check it by debugging?为什么不尝试捕获 Throwable 并通过调试来检查它?
try { /* code */ }
catch (Throwable t) { t.printStackTrace(); }
This solution tests EmployeeFileHandler and shows the error if eg the directory is not writable.此解决方案测试 EmployeeFileHandler 并在例如目录不可写时显示错误。 Run with
javac EmployeeFileHandler.java; java -ea EmployeeFileHandler
使用
javac EmployeeFileHandler.java; java -ea EmployeeFileHandler
运行javac EmployeeFileHandler.java; java -ea EmployeeFileHandler
javac EmployeeFileHandler.java; java -ea EmployeeFileHandler
to have it crash if assertion fails. javac EmployeeFileHandler.java; java -ea EmployeeFileHandler
如果断言失败,它会崩溃。 Ensure the Person class is also Serializable.确保 Person 类也是可序列化的。
import java.util.*;
import java.io.*;
public class EmployeeFileHandler implements Serializable {
public static void main(String[] args) {
ArrayList<Employees> employees = new ArrayList<Employees>();
for (int i = 0; i < 1000; i++) {
employees.add(new Employees("Name" + i, "Surname" + i, "" + i, 12345678));
}
writeDate(employees);
ArrayList<Employees> employees2 = new ArrayList<Employees>();
readData(employees2);
assert employees.size() == employees2.size();
for (int i = 0; i < 1000; i++) {
Employees e = employees2.get(i);
assert e.Name.equals("Name" + i);
assert e.Surname.equals("Surname" + i);
assert e.ID.equals("" + i);
assert e.MobNo == 12345678;
}
}
public static void readData(ArrayList<Employees> listIn) {
boolean endOfFile = false;
Employees temp;
try {
FileInputStream employeesFile = new FileInputStream("employee.obf");
ObjectInputStream employeesStream = new ObjectInputStream(employeesFile);
temp = (Employees) employeesStream.readObject();
while (endOfFile != true) {
try {
listIn.add(temp);
temp = (Employees) employeesStream.readObject();
} catch (EOFException e) {
endOfFile = true;
}
}
employeesStream.close();
}
catch (FileNotFoundException e) {
System.out.println("Employee file was not found");
} catch (IOException e) {
System.out.println("Employee file could not be read");
} catch (ClassNotFoundException e) {
System.out.println("Employee class was not found");
}
}
public static void writeDate(ArrayList<Employees> employee) {
try {
FileOutputStream EmployeesFile = new FileOutputStream("employee.obf");
ObjectOutputStream EmployeesStream = new ObjectOutputStream(EmployeesFile);
for (Employees employees : employee) {
EmployeesStream.writeObject(employees);
}
EmployeesStream.close();
} catch (IOException e) {
// System.out.println("Error occurred while saving");
e.printStackTrace();
}
}
}
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