將2個數組列表添加到另一個數組列表

Question

我有2這樣的arraylist，但我不確定如何將它們組合在一起。 我已經嘗試過Collections.copy（）和addAll方法，但是它無法正常工作，我想知道是否有任何方法可以將它們組合在一起成為另一個arraylist？ 我真正想要的是讓第一個arraylist存儲來自第二個arraylist的數據，因此每個Point里面都有幾行。 謝謝你們，也許你們可以給我一些建議。

 static ArrayList<Vertex> getPoints() {
      Scanner input = Reader(Vertex.airports);
      ArrayList<Vertex> result = new ArrayList<Vertex>();

      while(input.hasNext()){
          String point = input.nextLine();
          result.add(new Vertex(point));

      }
      input.close();
      return result;

  }

  static ArrayList<Edge> getlines(){
          Scanner input = Reader(Vertex.graph);
          ArrayList<Edge> result = new ArrayList<Edge>();

          while(input.hasNext()){
              String route = input.nextLine();
              result.add(new Edge(route));
          }
          input.close();
          return result;

      }

數據來自2個文本文件，該文件如下所示。 它們只是為了展示我在這里想要做什么。 （索引，名稱）

1 England
2 France

3荷蘭

（索引，開始，費用，結束）

1 1 2 2
2 1 3 1
3 1 6 3
4 1 7 3
5 2 1 2
6 2 3 1
7 2 4 1
8 2 5 2
9 2 6 2
10 3 1 1
11 3 2 1
12 3 4 1
13 3 8 1
14 3 10 2

多虧福特上尉完成了！

Answer 1

好的，我的理解是，第一個列表包含機場列表，第二個列表連接第一個列表中的機場。

如果要存儲對具有關聯點的線的引用，則需要圍繞包含另一個列表的點創建包裝。

class Airport {
    public Vertex point;
    public List<Edge> routes = new ArrayList<Edge>();

    public Airport(Vertex p){
        this.point = p;
    }
}

然后，當您加載列表時，您將執行以下操作：

static ArrayList<Airport> getAirports() {
    Scanner input = Reader(Vertex.airports);
    ArrayList<Vertex> result = new ArrayList<Vertex>();

    while(input.hasNext()){
        String point = input.nextLine();
        //  Note the small change on the next line
        result.add(new Airport(new Vertex(point)));

    }
    input.close();
    return result;
}

static ArrayList<Edge> getlines(){
    Scanner input = Reader(Vertex.graph);
    ArrayList<Edge> result = new ArrayList<Edge>();

    while(input.hasNext()){
        String route = input.nextLine();
        result.add(new Edge(route));
    }
    input.close();
    return result;

}

static void combineLists(List<Airport> airports, List<Edge> lines){
    for(Edge edge : lines){
        //  This is where we add the routes to both airports
        //  Since I don't know the structure of the edge class, I'm making a guess that you're using the integer indices that were described in the file to describe the endpoints. Note, however, that you will need to find a way to guarantee that they match the indices of the list of airports.
        airports.get(edge.p1).routes.add(edge);
        airports.get(edge.p2).routes.add(edge);
    }
}

Answer 2

我認為我可以改善其他答案。

更完整的解決方案如下所示：

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

public class Airport {
    public final int id;
    public String name;
    public List<Route> outboundRoutes = new ArrayList<Route>();
    public List<Route> inboundRoutes = new ArrayList<Route>();

    public double minDistance;
    public Airport previous;

    public Airport(int id, String name){
        this.id = id;
        this.name = name;
    }

    public static class Route {
        public final int id;
        public double cost;
        public Airport departure;
        public Airport destination;

        public Route(int id, double cost, Airport departure, Airport destination){
            this.id = id;
            this.cost = cost;
            this.departure = departure;
            this.destination = destination;
        }
    }


    public static Map<Integer,Airport> readAirports(Scanner input){
        Map<Integer,Airport> airports = new HashMap<Integer,Airport>();
        while(input.hasNext()){
            //  Using a map rather than a list simplifies the process of loading 
            //  your routes, and eliminates problems that would crop up if some
            //  airports are listed out of order or removed.
            Airport port = new Airport(input.nextInt(), input.next());
            airports.put(port.id, port);
        }
        return airports;
    }


    //  Note that the list of airports must be passed when loading the routes, 
    //  but that nothing is returned -- the routes are loaded directly 
    //  into the airports.
    public static void readRoutes(Scanner input, Map<Integer,Airport> airports){

        while(input.hasNext()){
            int id = input.nextInt();
            int departureId = input.nextInt();
            int destinationId = input.nextInt();
            double cost = input.nextDouble();

            if(!(airports.containsKey(departureId) && 
                    airports.containsKey(destinationId))){
                //  You'll have to decide how to handle a situation when a route 
                //  refers to airports that don't exist
                throw new RuntimeException(
                        "Undefined airport referenced in route #" + id);
            }

            Route route = new Route(id, cost, airports.get(departureId), 
                    airports.get(destinationId));
            route.departure.outboundRoutes.add(route);
            route.destination.inboundRoutes.add(route);
        }
    }

    public static Map<Integer,Airport> loadAirports() throws FileNotFoundException {
        Scanner inAirports = new Scanner(new File("airports.txt"));
        Scanner inRoutes = new Scanner(new File("routes.txt"));
        Map<Integer,Airport> airports = readAirports(inAirports);
        readRoutes(inRoutes, airports);
        return airports;
    }

    public static void main(String[] args){
        try {
            Map<Integer,Airport> airports = loadAirports();
            for(Airport port : airports.values()){
                System.out.println(port.name + " has " + port.inboundRoutes.size() + " inbound routes and " + port.outboundRoutes.size() + " outbound routes ");
                for(Route r : port.inboundRoutes){
                    System.out.println("\tin from " + r.departure.name + " at a cost of $" + r.cost);
                }
                for(Route r : port.outboundRoutes){
                    System.out.println("\tout to " + r.destination.name + " at a cost of $" + r.cost);
                }
            }

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

如果您想要一個簡單，簡單的答案，那么不進行某種嵌套就無法完成對ArrayList的處理。

由於您正在使用具有ID的數據，因此強烈建議您始終使用HashMap，這樣您就不必擔心數據排列不正確。 並且由於您具有元數據（機場名稱），因此創建這些類是對數據進行建模的好方法。

編輯：現在，代碼已更改為完全適合一個文件。 使用您提供的分別名為“ airports.txt”和“ routes.txt”的示例文件，它應該可以正常工作。 運行它時，應該獲得以下輸出：

England(LHR) has 4 inbound routes and 4 outbound routes 
    in from France(CDG) at a cost of $2.0
    in from Holland(AMS) at a cost of $1.0
    in from Portugal(LIS) at a cost of $3.0
    in from Iceland(KEF) at a cost of $3.0
    out to France(CDG) at a cost of $2.0
    out to Holland(AMS) at a cost of $1.0
    out to Portugal(LIS) at a cost of $3.0
    out to Iceland(KEF) at a cost of $3.0
France(CDG) has 5 inbound routes and 5 outbound routes 
    in from England(LHR) at a cost of $2.0
    in from Holland(AMS) at a cost of $1.0
    in from Germany(FRA) at a cost of $1.0
    in from Italy(LIN) at a cost of $2.0
    in from Portugal(LIS) at a cost of $2.0
    out to England(LHR) at a cost of $2.0
    out to Holland(AMS) at a cost of $1.0
    out to Germany(FRA) at a cost of $1.0
    out to Italy(LIN) at a cost of $2.0
    out to Portugal(LIS) at a cost of $2.0
Holland(AMS) has 5 inbound routes and 5 outbound routes 
    in from England(LHR) at a cost of $1.0
    in from France(CDG) at a cost of $1.0
    in from Germany(FRA) at a cost of $1.0
    in from Denmark(CPH) at a cost of $1.0
    in from Finland(HEL) at a cost of $2.0
    out to England(LHR) at a cost of $1.0
    out to France(CDG) at a cost of $1.0
    out to Germany(FRA) at a cost of $1.0
    out to Denmark(CPH) at a cost of $1.0
    out to Finland(HEL) at a cost of $2.0
Germany(FRA) has 4 inbound routes and 4 outbound routes 
    in from France(CDG) at a cost of $1.0
    in from Holland(AMS) at a cost of $1.0
    in from Italy(LIN) at a cost of $1.0
    in from Sweden(ARN) at a cost of $2.0
    out to France(CDG) at a cost of $1.0
    out to Holland(AMS) at a cost of $1.0
    out to Italy(LIN) at a cost of $1.0
    out to Sweden(ARN) at a cost of $2.0
Italy(LIN) has 3 inbound routes and 3 outbound routes 
    in from France(CDG) at a cost of $2.0
    in from Germany(FRA) at a cost of $1.0
    in from Portugal(LIS) at a cost of $3.0
    out to Portugal(LIS) at a cost of $3.0
    out to France(CDG) at a cost of $2.0
    out to Germany(FRA) at a cost of $1.0
Portugal(LIS) has 3 inbound routes and 3 outbound routes 
    in from England(LHR) at a cost of $3.0
    in from France(CDG) at a cost of $2.0
    in from Italy(LIN) at a cost of $3.0
    out to England(LHR) at a cost of $3.0
    out to France(CDG) at a cost of $2.0
    out to Italy(LIN) at a cost of $3.0
Iceland(KEF) has 1 inbound routes and 1 outbound routes 
    in from England(LHR) at a cost of $3.0
    out to England(LHR) at a cost of $3.0
Denmark(CPH) has 2 inbound routes and 2 outbound routes 
    in from Holland(AMS) at a cost of $1.0
    in from Norway(OSL) at a cost of $1.0
    out to Holland(AMS) at a cost of $1.0
    out to Norway(OSL) at a cost of $1.0
Norway(OSL) has 2 inbound routes and 2 outbound routes 
    in from Denmark(CPH) at a cost of $1.0
    in from Sweden(ARN) at a cost of $1.0
    out to Denmark(CPH) at a cost of $1.0
    out to Sweden(ARN) at a cost of $1.0
Finland(HEL) has 2 inbound routes and 2 outbound routes 
    in from Holland(AMS) at a cost of $2.0
    in from Sweden(ARN) at a cost of $1.0
    out to Sweden(ARN) at a cost of $1.0
    out to Holland(AMS) at a cost of $2.0
Sweden(ARN) has 3 inbound routes and 3 outbound routes 
    in from Germany(FRA) at a cost of $2.0
    in from Norway(OSL) at a cost of $1.0
    in from Finland(HEL) at a cost of $1.0
    out to Germany(FRA) at a cost of $2.0
    out to Norway(OSL) at a cost of $1.0
    out to Finland(HEL) at a cost of $1.0