Question

一群朋友和我正在进行秘密的圣诞老人交流，我决定制作一个程序来随机化并打印一份我将拥有的主列表，以获得乐趣。这是我到目前为止所拥有的。我对第String random1 = sList.get(myRandomizer.nextInt(sList.size()));行

有疑问

它给出的错误是我做了不兼容的类型，但我很确定它会返回它应该做的事情吗？

这是我的初级课程

import java.io.Serializable;
public class SpecifiedData implements Serializable
{
   private String name;
   public SpecifiedData(String name)
   {
       this.name = name;
   }   
   public String getName()
   {
       return name;
   }   
}

这是我的测试类，我的错误是

import java.util.*;
import java.io.*;
public class Randomizer
{
    public static void main(String[] args) throws IOException, ClassNotFoundException
    {
        Random myRandomizer = new Random();
        boolean done = false;
        ArrayList<SpecifiedData> sList = new ArrayList<SpecifiedData>();
        File sFile = new File("Participants.dat");
        if(sFile.exists())
        {
            FileInputStream myFIS = new FileInputStream(sFile);
            ObjectInputStream sIn = new ObjectInputStream(myFIS);
            sList = (ArrayList<SpecifiedData>)sIn.readObject();
            sIn.close();
        } 
        do
        {
            Scanner myScanner = new Scanner(System.in);        
            while (!done)
            {
                System.out.println("1 - add a person");
                System.out.println("2 - display all people");
                System.out.println("3 - delete person");
                System.out.println("4 - randomize");
                System.out.println("5 - exit");
                int choice = Integer.parseInt(myScanner.nextLine());
                if (choice == 1)
                {
                    System.out.print("Enter person's name: ");
                    String participantsName = myScanner.nextLine();
                    SpecifiedData mySpecifiedData = new SpecifiedData(participantsName);
                    sList.add(mySpecifiedData);
                }
                else if (choice == 2)
                {
                    for(int i = 0; i < sList.size(); i++)
                        System.out.println(sList.get(i).getName());
                }
                else if (choice == 3)
                {
                    System.out.println("Enter persons name: ");
                    String participantsName = myScanner.nextLine();
                    for(SpecifiedData mySpecifiedData : sList)
                    {
                        if(mySpecifiedData.getName().equals(participantsName))
                        {
                            sList.remove(mySpecifiedData);
                            break;
                        }
                    }
                }
                else if (choice == 4)
                {
                    for(int i = 0; i < (sList.size()/2); i++)
                    {
                    for(SpecifiedData mySpecifiedData : sList)
                    {
                        String random1 = sList.get(myRandomizer.nextInt(sList.size()));
                        if(mySpecifiedData.getName().equals(random1))
                        {
                            System.out.println(random1 + "     ");
                            sList.remove(random1);
                            break;
                        }
                        String random2 = sList.get(myRandomizer.nextInt(sList.size()));
                        if(mySpecifiedData.getName().equals(random2))
                        {
                            System.out.print(random2);
                            sList.remove(random2);
                            break;
                        }
                    }
                    }    
                }
                else if(choice == 5)
                {
                    done = true;
                }    
                else
                    System.out.println("Invalid menu choice!");
            }
            System.out.println("Goodbye!");
        }while(!done);
        FileOutputStream myFOS = new FileOutputStream(sFile);
        ObjectOutputStream sOut = new ObjectOutputStream(myFOS);
        sOut.writeObject(sList);
        sOut.close();
    }    
}

Answer 1

sList被声明为包含SpecifiedData类型对象的ArrayList。在该行上，您将从列表中获取一个对象并尝试将其分配给String。您需要将其分配给SpecifiedData。

 SpecifiedData random1 = sList.get(myRandomizer.nextInt(sList.size()));

Answer 2

sList是SpecifiedData类型的列表，而不是String，因此此错误完全正常。顺便说一下，你正在从你正在遍历的列表中删除元素......糟糕的主意。我没有仔细查看你的代码，但有一件事是肯定的：你必须改进它。

然后选择从arraylist中删除随机元素

2 个答案: