從另一個類打印ArrayList

Question

我有另一個類中的arrayList的打印函數。每當我調用它時，它只顯示一個空的ArrayList。我究竟做錯了什麼？我幾乎模擬使用線程的電梯，只是將樓層添加到arrayList，然後需要對它們進行排序。我只是想打印數組來看看它是否有序。

import java.util.Random; 
import java.util.concurrent.Semaphore; 

public class Threads { 

    public static int RandomFloor(){ 
     Random random = new Random(); 
     int floor = random.nextInt(6) + 2; 
     return floor; 
    } 
    public static void main(String[] args) throws Exception { 

     Semaphore sem = new Semaphore(0); 
     //Random number for floors 

     Elevator elevator1 = new Elevator(); 

     //Creates the first set of threads and assigns the floor using random number generator defined at the top. 
     Thread myThread1 = new Thread(new Driver(1,RandomFloor())); 
     Thread myThread2 = new Thread(new Driver(2,RandomFloor())); 
     Thread myThread3 = new Thread(new Driver(3,RandomFloor())); 
     Thread myThread4 = new Thread(new Driver(4,RandomFloor())); 
     Thread myThread5 = new Thread(new Driver(5,RandomFloor())); 
     Thread myThread6 = new Thread(new Driver(6,RandomFloor())); 
     Thread myThread7 = new Thread(new Driver(7,RandomFloor())); 
     Thread elevator = new Thread(new Elevator()); 

     //Start first set of threads 
     myThread1.start(); 
     myThread1.join(); 
     myThread2.start(); 
     myThread3.start(); 
     myThread4.start(); 
     myThread5.start(); 
     myThread6.start(); 
     myThread7.start(); 

     elevator1.printFloors(); 

     sem.acquire(); 


} 
} 

其中包含ArrayList和打印功能電梯類

import java.util.*; 
    public class Elevator implements Runnable 
{ 

    List<Integer> floors = new ArrayList<Integer>(); 
    int floor; 
    //add floors into Arraylist 
    public void addFloors(int floor) 
    { 

    this.floor=floor; 
     floors.add(floor); 

     System.out.println("Added to floor array\n"); 

     System.out.println(floors); 
    } 

    public void run() 
    { 

    } 


    public void sortFloors() 
    { 
     Collections.sort(floors); 
    } 

    public void printFloors() 
    { 
     //System.out.println(floors); 
    } 
} 

Answer 1

您可以創建一個新的電梯線程像這樣的地板的隨機數：

Elevator elevator1 = new Elevator(); 
int numberOfFloors = RandomFloor(); 
for(int i = 1; i <= numberOfFloors; i++) 
    elevator1.addFloors(i); 

這將產生一個來自RandomFloor（）方法的隨機數並將許多整數添加到Elevator對象中的floors數組中。

像其他人指出，你的代碼中有一些錯誤，比如甚至沒有調用addFloors方法，並printFloors無碼

---

如果你想安裝的電梯對象在隨機地板開始然後給它一些隨機數字地面模擬客戶呼叫，那麼你可以修改你的代碼是這樣的：

電梯類：

public class Elevator implements Runnable 
{  
    private List<Integer> floors = new ArrayList<Integer>(); 
    private int startingFloor = 0; 

    //add floor into Arraylist 
    public void addFloor(int floor) 
    { 
     floors.add(floor); 
     System.out.println("Added to floor array\n"); 
     System.out.println(floors); 
    } 

    public void setStartingFloor(int floor){ 
     this.startingFloor = floor; 
    } 

    public void run() 
    { 

    } 

    public void sortFloors() 
    { 
     Collections.sort(floors); 
    } 

    public void printFloors() 
    { 
     System.out.println(floors); 
    } 
} 

主要方法：

Elevator elevator1 = new Elevator(); 
elevator1.setStartingFloor(RandomFloor()); 

int numberOfElevatorCalls = 50; 
for(int i = 0; i < numberOfElevatorCalls, i++){ 
    elevator1.addFloor(RandomFloor()); 
} 

// sort 
elevator1.sortFloors(); 

// print 
elevator1.printFloors();