java - 如何在java中使用序列化删除特定员工

Question

我想删除用户输入其详细信息的特定员工。我在 java 中使用序列化。删除操作没有按照我想要的方式执行。我想删除用户输入其详细信息的员工。但它会删除所有员工

import java.io.*;
import java.util.*;

  public class SerializationDemo {
    public static void main(String[] args) throws IOException, ClassNotFoundException{
        //choice provided to the user
        System.out.println("Welcome To Employee Management System");
        System.out.println("Enter your choice");
        System.out.println("Enter 1:->show employees");
        System.out.println("Enter 2:->Create new employee");
        System.out.println("Enter 3:->Delete employee");
        System.out.println("Enter 4:->quit");

        Scanner in = new Scanner(System.in);
        int choice = in.nextInt();

        ArrayList<Myclass> object1 = new ArrayList<Myclass>();
        //insert operation
        if(choice==2){
            try{
                String str1;
                String str2;
                BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
                System.out.println("Enter number of employees you want to add");
                Scanner in1 = new Scanner(System.in);
                int num = in1.nextInt();

                //ArrayList<Myclass> object1 = new ArrayList<Myclass>();

                for(int i=0;i<num;i++){

                    str1 = br.readLine();
                    str2 = br.readLine();
                    object1.add(new Myclass(str1,str2));
                }

                FileOutputStream fos = new FileOutputStream("Myfile.txt");
                ObjectOutputStream oos = new ObjectOutputStream(fos);

                oos.writeObject(object1);
                oos.flush();
                oos.close();
            }
            catch(Exception e){
                System.out.println("exception");
                e.printStackTrace();
                System.exit(0);
            }
        }
        //show operation
        if(choice==1){
            try{
                FileInputStream  fis = new FileInputStream("Myfile.txt");
                ObjectInputStream ois = new ObjectInputStream(fis);
                ArrayList object2 = (ArrayList)ois.readObject();

                ois.close();
                System.out.println("employee details "+" "+object2);
            }
            catch(Exception e){
                e.printStackTrace();
            }

        }

        if(choice==3){
            System.out.println("Enter name and department of employee you want to delete");
            try {

                String str3;
                String str4;
                BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));
                str3 = br1.readLine();
                str4 = br1.readLine();

                /*FileInputStream  Fs = new FileInputStream("Myfile");
                ObjectInputStream Os = new ObjectInputStream(Fs);
                ArrayList<Myclass> object3 = (ArrayList<Myclass>)Os.readObject();*/

                object1.remove(new Myclass(str3,str4));

                FileOutputStream fs = new FileOutputStream("Myfile.txt");
                ObjectOutputStream os = new ObjectOutputStream(fs);
                os.writeObject(object1);
                os.flush();
                os.close();

            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }

        }
        //exit operation
        if(choice==4){
            System.exit(0);
        }

    }
}


    class Myclass implements Serializable{
        String name;
        String dname;
        public Myclass(String name,String dname){
            this.name = name;
            this.dname = dname;
        }
        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getDepartment() {
            return dname;
        }

        public void setDepartment(String dname) {
            this.dname = dname;
        }
        public String toString(){
            return "name = "+" "+name+","+" "+"department = "+" "+dname;
        }
    }

Answer 1

我在这里看到两个问题。

• 在choice=3 中，您需要先将对象反序列化为object1 列表，然后再删除对象并重新序列化。
• MyClass 中需要equals() 和hashCode() 方法。 list.remove() 不会，因为它无法从列表中找到您提供的对象。

Answer 2

@AmitChotaliya 解释清楚了

这是从 ArrayList 中删除对象的示例

首先需要反序列化

FileInputStream  Fs = new FileInputStream("Myfile.txt");
ObjectInputStream Os = new ObjectInputStream(Fs);
ArrayList<Myclass> object3 = (ArrayList<Myclass>)Os.readObject();

然后删除它，但这是快速失败

for(int index = 0; i < object3.size(); i++)
{
   if(object3.get(i).getName().equals(str3) && object3.get(i).getDepartment().equals(str4))
   {
      object3.remove(index);
      break;
   }
}

但是如果你想用 Fail Safe 移除它

Iterator itr = object3.iterator();

while(itr.hasNext()) {
   Myclass element = (Myclass) itr.next();
   if(element.getName().equals(str3) && element.getDepartment().equals(str4))
   {
       itr.remove();
       break;
   }
}