java - 在 Java 中声明全局 arrayList

Question

如何声明可从所有方法访问的全局 ArrayList。我尝试在 main、class 和其他各个地方声明它。

 public static void InitializeTrips() {
        public static List<Trip> TripList = new ArrayList<>();
        TripList.add(new Trip(1, "NGP", "MUM", 3000, 1200, 1330));
        TripList.add(new Trip(1, "MUM", "NGP", 3500, 1400, 1530));
    }
public static void AddTrips() {
        Scanner inpt = new Scanner(System.in);
        int trpindx;String str;String end;int cst;int tmes;int tmee;
        System.out.println("Please input the following :-");
        System.out.print("Trip Index : "); trpindx = inpt.nextInt(); ;System.out.println("");
        System.out.print("Source     : "); str = inpt.next(); ;System.out.println("");
        System.out.print("End        : "); end = inpt.next(); ;System.out.println("");
        System.out.print("Cost       : "); cst = inpt.nextInt(); ;System.out.println("");
        System.out.print("Departure  : "); tmes = inpt.nextInt(); ;System.out.println("");
        System.out.print("Arrival    : "); tmee = inpt.nextInt(); ;System.out.println("");

}

public  static  void PrintTrips() {
    System.out.print("Index     Source     Destination     Depature     Arrival     Cost    ");
    .TripList.forEach(TripList -> {
        System.out.println( ( TripList.getTRPINDX() )+ "     " +(TripList.getSTR)+"     "+(TripList.getEND)+"     "+(TripList.getCST)+"     "+(TripList.getTMEs)+"     "+(TripList.getTMEe)+"     "+(TripList.getDUR)+");
    });

Answer 1

请尝试这个示例代码:-

package design.pattern;

import java.util.ArrayList;

public class GlobalAccessVariables {
      public ArrayList<Trip> trips;

      private GlobalAccessVariables() {
        trips = new ArrayList<Trip>();
      }

      private static GlobalAccessVariables instance;

      public static GlobalAccessVariables getInstance() {
        if (instance == null) 
            instance = new GlobalAccessVariables();
        return instance;
      }

}

在任何类中访问它:

GlobalAccessVariables instance = GlobalAccessVariables.getInstance();
ArrayList tripsList = instance.trips;
tripsList.add("add trip here")

希望它对你有用