我有2个像这样的arraylist，但我不知道如何将它们组合在一起。我已经尝试了Collections.copy（）和addAll方法，但它不会工作，我想知道是否有任何方法可以将它们组合成另一个arraylist？我真正想要的是让第一个arraylist存储来自第二个arraylist的数据，所以每个Point里面都会有几行。也许你们可以给我一些关于如何做到这一点的建议，谢谢。
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;
}
数据来自2个文本文件，文件如下所示。它们只是展示我在这里尝试做什么的一部分。 （索引，名称）
1 England
2 France
（索引，开始，成本，结束）
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
答案 0 :(得分：1)
好的，我的理解是第一个列表包含机场列表，第二个列表连接第一个列表中的机场。
如果要存储对具有关联点的线的引用，则需要围绕包含其他列表的点创建包装。
class Airport {
public Vertex point;
public List<Edge> routes = new ArrayList<Edge>();
public Airport(Vertex p){
this.point = p;
}
}
然后，当您加载列表时，您会执行以下操作：
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);
}
}
答案 1 :(得分：0)
我想我可以改进其他答案。
更完整的解决方案如下所示：
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();
}
}
}
如果你想要一个简单直接的答案，那么在没有进行某种嵌套的情况下，你想要用ArrayLists做什么是不可能做到的。
由于您正在使用具有ID的数据，因此我强烈建议您使用HashMap，这样您就不必担心数据不完整。由于您拥有元数据（机场名称），因此创建这些类是建模数据的好方法。
编辑：代码现已更改为适合一个文件。使用您提供的示例文件分别称为“airports.txt”和“routes.txt”，它应该可以正常工作。当你运行它时，你应该得到以下输出：
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