java - 使用泛型实现数组列表，其中列表的最大大小是动态的

Question

我想问一下有没有人知道如何解决这个问题。 我收到此消息:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
    at Main.add(Main.java:40)  // it is for: myList[actSize++] = object;
    at Main.main(Main.java:127) //it is for: ob.add(str+str1+str2); 

我想问一下我现在做的事情对吗？我想构建一个使用泛型的程序，其中包含以下方法:添加、删除、获取、包含和大小方法。但是当我构建程序时，我发现泛型无法创建数组，因此我使用了本网站另一篇文章中的内容:[如何:泛型数组创建并使用弱类型(未经检查)。因此，该程序的主题是某人在控制台中输入他的名字、姓氏和电话号码，然后将其放入泛型数组中，以便我可以将其保存到一个对象中，然后保存到特定位置。之后，程序会动态增加阈值，以便用户拥有大量联系人。然后他会被告知他的联系人是否被重复，并将立即删除。之后他会被询问是否要删除契约(Contract)，然后程序统计全部结束，直到用户完成他的工作(添加契约(Contract))。

我很高兴听到一些意见。

(如果我听不懂，我很抱歉我的英语。)

import java.util.Arrays;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main < T >
{

    private Object[] myList;
    public static int actSize = 0;

    public Main(int s)
    {
        myList = new Object[s];
    }

    public T Array(int i)
    {
        @SuppressWarnings("unchecked")
        final T t = (T) myList[i];
        return t;
    }

    public void add(T object) //end
    {
        if (myList.length - actSize <= 5)
        {
            myList = Arrays.copyOf(myList, myList.length * 2);
            System.out.println("\nNew length: " + myList.length);
        }

        myList[actSize++] = object;
    }

    public void add(T object, int position) //end
    {
        myList[position++] = object;
    }

    public boolean remove(T object) //end
    {
        if (myList[actSize].equals(object))
        {
            myList[actSize] = myList[actSize - 1];
            return true;
        }
        else
            return false;
    }

    public void remove(int position) //end
    {
        myList[position] = myList[position - 1];
    }

    @SuppressWarnings("unchecked")
    public T get(int index) //end
    {
        if (index < actSize)
        {
            return (T) myList[index];
        }
        else
        {
            throw new ArrayIndexOutOfBoundsException();
        }
    }

    public boolean contains(T object) //end
    {
        if (myList[actSize].equals(object))
        {
            return false;
        }
        else
            myList[actSize] = myList[actSize - 1];

        return true;
    }

    public int size() //end
    {
        return actSize;

    }

    @SuppressWarnings("unchecked")
    public static void main(String[] args)
    {
        @SuppressWarnings("rawtypes")
        Main ob = new Main(actSize);
        String str, str1, str2;

        try
        {
            BufferedReader br = new BufferedReader(new InputStreamReader(System. in ));

            while (true)
            {
                System.out.print("Do you want to add a contact? press any key to continue or n to exit :");
                String str5 = br.readLine();

                if ("n".equalsIgnoreCase(str5))
                {
                    System.exit(1);
                }

                System.out.print("Enter your First Name :");
                str = br.readLine();

                System.out.print("Enter your Last Name :");
                str1 = br.readLine();

                System.out.print("Enter your Phone Number :");
                str2 = br.readLine();

                ob.add(str + str1 + str2);
                ob.add(str + str1 + str2, actSize);

                if (ob.contains(str + str1 + str2) == true)
                {
                    System.out.println("The contact you entered is duplicated");
                    ob.remove(ob.contains(str + str1 + str2));
                    System.out.println("The contact has been removed");
                }

                System.out.print("Do you want to add contracts? press y to continue :");
                String str3 = br.readLine();
                System.out.println("You just entered:" + str3);

                if ("y".equalsIgnoreCase(str3))
                {
                    System.out.print("Which contract do you wish to be removed?");
                    String str4 = br.readLine();

                    if (str4.equals(actSize))
                    {
                        ob.remove(actSize);
                        System.out.println("The contact has been deleted.");
                    }
                }
            }
        }
        catch (IOException e)
        {
            e.printStackTrace();
        }
    }

}

Answer 1

为什么不使用 List<YourGenericType> list = new ArrayList<YourGenericType>(); 现在您可以调用list.size(); list.add(); list.set(); list.get();... 。 ArrayList 也具有动态大小。

我建议这样做:删除您的 Main 并将您的 main 方法更改为如下所示:

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

public class Test {

    public static void main(String[] args) {

        List<String> list = new ArrayList<String>();
        String str, str1, str2;
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    System.in));
            while (true) {

                System.out
                        .print("Do you want to add a contact? press any key to continue or n to exit :");
                String str5 = br.readLine();

                if ("n".equalsIgnoreCase(str5)) {
                    System.exit(1);
                }

                System.out.print("Enter your First Name :");
                str = br.readLine();

                System.out.print("Enter your Last Name :");
                str1 = br.readLine();

                System.out.print("Enter your Phone Number :");
                str2 = br.readLine();

                StringBuilder sb = new StringBuilder();
                sb.append(str + str1 + str2);

                for (int i = 0; i < list.size(); i++) {
                    String s = list.get(i);
                    if (s.equals(sb.toString())) {
                        System.out.println("Duplicate");
                        list.remove(i);
                    }
                }
                list.add(sb.toString());

                System.out
                        .print("Do you want to add contracts? press y to continue :");
                String str3 = br.readLine();
                System.out.println("You just entered:" + str3);

                if ("y".equalsIgnoreCase(str3)) {
                    System.out
                            .print("Which contract do you wish to be removed?");
                    String str4 = br.readLine();

                    int index = Integer.parseInt(str4);
                    if (index < list.size() && index > 0) {
                        list.remove(index);
                    }

                }

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

}