如何从ArrayList的ArrayList中打印字符串

如何解决如何从ArrayList的ArrayList中打印字符串

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


class Adventurers
{
    public static void main (String[] args) throws java.lang.Exception
    {
    public static void main (String[] args) throws java.lang.Exception{
            
    ArrayList<String> friends = new ArrayList<>(Arrays.asList(new String[]{"Danny","Benni","Marcus","Pat"}));
    ArrayList<String> places = new ArrayList<>(Arrays.asList(new String[]{"Paris","Brasil","Miami","Jamaica"}));
    ArrayList<String> gifts = new ArrayList<>(Arrays.asList(new String[]{"Snacks","Photos","Instrument","Whine"}));
    ArrayList<String> events = new ArrayList<>(Arrays.asList(new String[]{"Zombie Tag ","Bar tour"}));
    ArrayList<String> people = new ArrayList<>(Arrays.asList(new String[]{"Karen "," Ryu "," Darth Vader"}));
    ArrayList<String> animals = new ArrayList<>(Arrays.asList(new String[]{"Dog "," Cat "," Bird "}));
    
    ArrayList[] objectives = new ArrayList<>(Arrays.asList(new String[] {places,gifts,events,people,animals});
    
    
    

    

    for(String friend : friends){
        System.out.println(objectives.get(rand.nextInt(objectives.size())).get(rand.nextInt(this.size)));
        
     }
}
    }
}

你好，我正在尝试从主ArrayList的ArrayList打印随机消息，因为我正在尝试打印每个朋友的目标列表（另一个列表）。我想知道如何单独打印它们，尽管我想知道是否可以从主ArrayList打印字符串。

解决方法

您的代码有多个小语法错误。我已经修复了它们：

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


public class Adventurers
{
    public static void main (String[] args) throws java.lang.Exception{
            
    ArrayList<String> friends = new ArrayList<>(Arrays.asList(new String[]{"Danny","Benni","Marcus","Pat"}));
    ArrayList<String> places = new ArrayList<>(Arrays.asList(new String[]{"Paris","Brasil","Miami","Jamaica"}));
    ArrayList<String> gifts = new ArrayList<>(Arrays.asList(new String[]{"Snacks","Photos","Instrument","Whine"}));
    ArrayList<String> events = new ArrayList<>(Arrays.asList(new String[]{"Zombie Tag ","Bar tour"}));
    ArrayList<String> people = new ArrayList<>(Arrays.asList(new String[]{"Karen "," Ryu "," Darth Vader"}));
    ArrayList<String> animals = new ArrayList<>(Arrays.asList(new String[]{"Dog "," Cat "," Bird "}));
    
    ArrayList[] objectives = new ArrayList<>(Arrays.asList(new String[] {places,gifts,events,people,animals}));
    
    
    

    

    for(String friend : friends){
        System.out.println(objectives.get(rand.nextInt(objectives.size())).get(rand.nextInt(this.size)));
        
     }
}
}

然后您可以参考this question来解决问题。

,

您正在使用什么版本的Java，从版本8开始，您可以使用以下流：

String value = friends.stream().flatMap(e -> e.stream()).findAny().get();

,

您的代码有多个小语法错误。我认为您需要了解更多有关Java的知识。

public static void main (String[] args){

    Random rand = new Random();
    ArrayList<String> friends = new ArrayList<>(Arrays.asList("Danny","Pat"));
    ArrayList<String> places = new ArrayList<>(Arrays.asList("Paris","Jamaica"));
    ArrayList<String> gifts = new ArrayList<>(Arrays.asList("Snacks","Whine"));
    ArrayList<String> events = new ArrayList<>(Arrays.asList("Zombie Tag ","Bar tour"));
    ArrayList<String> people = new ArrayList<>(Arrays.asList("Karen "," Darth Vader"));
    ArrayList<String> animals = new ArrayList<>(Arrays.asList("Dog "," Bird "));
    List[] objectives = new List[]{Arrays.asList(places,animals)};

    for(String friend : friends){
        System.out.println(objectives[rand.nextInt(objectives.length)].get(rand.nextInt(friend.length())));
    }
}

,

import java.util.Arrays;
import java.util.List;
import java.util.Random;

public class Main {

    public static void main(String[] args) {
        Random rand = new Random();
        List<String> friends = Arrays.asList("Danny","Pat");
        List<String> places = Arrays.asList("Paris","Jamaica");
        List<String> gifts = Arrays.asList("Snacks","Whine");
        List<String> events = Arrays.asList("Zombie Tag","Bar tour");
        List<String> people = Arrays.asList("Karen","Ryu","Darth Vader");
        List<String> animals = Arrays.asList("Dog","Cat"," Bird");

        List<List<String>> lists = Arrays.asList(places,animals);

        for (String friend : friends) {
            System.out.print(friend + ": ");
            boolean isFirst = false;
            for (List<String> list : lists) {
                if (!isFirst) {
                    isFirst = true;
                } else {
                    System.out.print(",");
                }
                System.out.print(list.get(rand.nextInt(list.size())));
            }
            System.out.println();
        }
    }
}

老实说，我花了更多时间弄清楚您的初衷。经过大量的猜测之后，我认为这就是您想要的。

存在一些语法错误和一些不必要的嵌套函数调用，我为您删除了它们。请仔细研究差异。

此外，我认为我们都需要了解一些内容：如果需要使用某个内置对象，请先弄清楚其内置方法；如果要调用内置方法，请先了解其参数。