使用来自其他类的输入

Question

现在我有3个类。火车，旅行车和乘客。在火车类

public class Train 
    { 
     private int seatNum = 30 + (int) (Math.random() * ((40 - 30) + 1)); //Random number of seats 
     private int wagonNum = 5 + (int) (Math.random() * ((10 - 5) + 1));//Random number of wagons 

     public Train() 
     { 
      PassWagon[] wagons = new PassWagon[wagonNum];//here I created an array with random wagon numbers. 

      for (int i = 0; i < wagonNum; i++) 
      { 
       wagons[i] = new PassWagon(seatNum); // I added PassWagon objects to that array. I need to access "seatnum" in the PassWagon class. 

      } 
     } 

    } 

和

public class PassWagon 
{ 
private int wagonseats ; 

Passenger[] rowA = new Passenger[wagonseats]; //I created 2 "Passenger" arrays. Problem is, wagonseats variable has nothing. "seatNum" variable from other class gets initiated at Constructor. 
Passenger[] rowB = new Passenger[wagonseats]; 
    public PassWagon(int seat) 
    { 
     this.wagonseats = seat; 

     for (int i = 0; i < seats; i++) 
     { 
      rowA[i] = new Passenger(); //I get an out of bounds error here because this array has nothing in it. 
      rowB[i] = new Passenger(); 
     } 
    } 

我想要得到的 “seatNum” 变量并使用它来创建行rowA和rowB中的阵列。我尝试过几件事：

• 我在PassWagon类中生成了随机数，但是这次每个货车对象都有不同数量的座位。我希望所有的货车都有相同数量的座位。

• 我在构造函数里面创建了rowA和rowB数组，这次我无法在构造函数外声明rowA和rowB数组。

  有没有人有任何想法？

Answer 1

你应该创建的rowA和rowB变量领域，构造之外，但是初始化他们在构造函数中，一旦你的参数seat（实际上是席位法官数量来自其他班级）。

public class PassWagon { 
    private int wagonseats ; 

    Passenger[] rowA; // Just create, don't initialize yet 
    Passenger[] rowB; 

    public PassWagon(int seat) { 
     this.wagonseats = seat; 
     rowA = new Passenger[wagonseats]; 
     rowB = new Passenger[wagonseats]; 

     for (int i = 0; i < wagonseats; i++) { 
      rowA[i] = new Passenger(); 
      rowB[i] = new Passenger(); 
     } 
    } 
} 

你的问题是，当你在构造函数之前初始化它们，wagonseats刚刚创建的，因此包含0。所以你正在创建一个零成员数组。创建后无法更改，因此只有在拥有正确的编号时才能创建它。

顺便说一下，如果有两排，我想wagonseats实际上应该是seat/2，不是吗？或者至少，阵列的大小和循环的极限应该是seat/2。