反序列化 ArrayList：[unchecked] 需要未经检查的转换：ArrayList<employee> 发现：ArrayList</employee>

Question

我正在尝试序列化和反序列化一个 Java 应用程序。 它正在工作，但我想知道我是否正确地执行了这个过程。 我正在序列化 ArrayList； 这是正确的方法还是我应该序列化 Employee 类，但考虑到我们可能有很多员工，我将如何处理？

我这样做的方式导致了这个错误，我想摆脱它：

serialTest.java:40: 警告: [unchecked] 未经检查的转换员工 = (ArrayList) ois.readObject(); 要求：ArrayList 找到：ArrayList 1 警告

这是 Employee 类：package serialTest； 导入 java.io.Serializable；

public class Employee implements Serializable {

    int id;
    String firstName;
    String lastName;

    public Employee(int id, String firstName, String lastName) {
        super();
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
    }
}

这是主要课程：

package serialTest;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;

public class serialTest {

    static ArrayList<Employee> employees = new ArrayList<>();

    public static void main(String[] args) {
        if (args.length > 0) {
            deSerialize();
        } else {
            employees.add(new Employee(1, "John", "Doe"));
            employees.add(new Employee(2, "Jane", "Doe"));
            serialize();
        }
    }

    private static void serialize() {
        System.out.println("Serializing...");
        try {
            try (FileOutputStream fos = new FileOutputStream("employeeData"); ObjectOutputStream oos = new ObjectOutputStream(fos)) {
                oos.writeObject(employees);
            }
        } catch (IOException ioe) {
        }
    }

    private static void deSerialize() {
        System.out.println("DeSerializing...");
        try {
            try (FileInputStream fis = new FileInputStream("employeeData");
                    ObjectInputStream ois = new ObjectInputStream(fis)) {

                employees = (ArrayList) ois.readObject();

            }
        } catch (IOException ioe) {
            System.out.println("File problems");
            return;
        } catch (ClassNotFoundException c) {
            System.out.println("Class problems");
            return;
        }

        for (Employee info : employees) {
            System.out.println(info);
        }
    }
}

Answer 1

您将不得不取消该警告。 由于类型擦除，Java 不知道实际的泛型类型。

Answer 2

我想出了一个解决方案。 将不胜感激一些评论。

package serialTest;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Arrays;

public class serialTest {

    static ArrayList<Employee> employees = new ArrayList<>();

    public static void main(String[] args) {
        if (args.length > 0) {
            deSerialize();
        } else {
            employees.add(new Employee(1, "John", "Doe"));
            employees.add(new Employee(2, "Jane", "Doe"));
            serialize();
        }
    }

    private static void serialize() {
        System.out.println("Serializing...");
        try {
            try (FileOutputStream fos = new FileOutputStream("employeeData"); 
                    ObjectOutputStream oos = new ObjectOutputStream(fos)) {
                oos.writeObject((Employee[]) employees.toArray(new Employee[employees.size()]));
            }
        } catch (IOException ioe) {
        }
    }

    private static void deSerialize() {
        System.out.println("DeSerializing...");
        try {
            try (FileInputStream fis = new FileInputStream("employeeData");
                    ObjectInputStream ois = new ObjectInputStream(fis)) {

                employees.addAll(Arrays.asList((Employee[]) ois.readObject()));
            }
        } catch (IOException ioe) {
            System.out.println("File problems");
            return;
        } catch (ClassNotFoundException c) {
            System.out.println("Class problems");
            return;
        }

        for (Employee info : employees) {
            System.out.println(info);
        }
    }
}