Question

我有一些元素path = [1, 2, 5, 7]的ArrayList。现在我想从这些元素中获取值：

1,2 
2,5
5,7

我为此目的使用了列表迭代器，但我得到的是：

我看到了这个答案： how to get all combination of an arraylist? 但我不需要像这样的所有组合。

我的代码是：

public class iterator {

public static void main(String[] args){
    ArrayList<String> path=new ArrayList<>();
    path.add("1");
    path.add("2");
    path.add("5");
    path.add("7");

    System.out.println(path);
    ListIterator<String> itr =  path.listIterator();  
    while(itr.hasNext())
    {
        System.out.println(itr.next()+ "," + itr.next());
        System.out.println(itr.previous()+ "," + itr.next());
    }

}

}

我的问题是如何才能获得所需的结果？

Answer 1

for (int i = 0; i < path.size() - 1; i++) {
    System.out.println(path.get(i) + "," + path.get(i + 1));
}

Answer 2

您可以尝试使用传统的for循环计数器来实现此目的：

for (int i = 0; i < path.size() - 1; i++) {
    System.out.println(path.get(i) + ", " + path.get(i+1));
}

Answer 3

问题是ListIterator获取下一个元素并提升光标。要使用while (itr.nextIndex() + 1 < path.size()) { System.out.println(itr.next() + "," + itr.next()); itr.previous(); // back up 1 to get the duplicate }，您可以这样做：

using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.Text;
using System.Timers;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;

namespace bicmwinservice
{
    public partial class Service1 : ServiceBase
    {
        public Service1()
        {
            InitializeComponent();
        }

        public void OnDebug() 
        {
            OnStart(null);
        }

        private Timer count;

        protected override void OnStart(string[] args)
        {

            count = new Timer(1 * 60 * 1000);  // 5 minutes expressed as milliseconds
            count.Elapsed += new ElapsedEventHandler(OnTimerElapsed);
            count.AutoReset = true;
            count.Start();

        }

        protected override void OnStop()
        {
            System.IO.File.Create(AppDomain.CurrentDomain.BaseDirectory + "OnStop.txt");          
        }

        private void OnTimerElapsed(object sender, ElapsedEventArgs e) 
        {


                DateTime time = DateTime.Now;
                DateTime date = DateTime.Now;


                string connString = "Server=mysql1003.mochahost.com;Database=snowphil_tester;Uid=snowphil_test;password=snowphil_test;";
                MySqlConnection conn = new MySqlConnection(connString);
                MySqlCommand command = conn.CreateCommand();


                StreamReader read = new StreamReader(@"C:\brcode.txt", Encoding.Default);

                command.CommandText = "Update branch_monitor SET `date`='" + date.ToString("yyyy'-'MM'-'dd") + "', `time`= '" + time.ToString("HH':'mm':'ss") + "' WHERE branch_code='" + read + "'";
                conn.Open();
                command.ExecuteNonQuery();

                conn.Close();

        }

    }
}

如何从arraylist获得所需的两个数字组合？

3 个答案: