Question

原谅我，我是Java新手！而且对于一个大学项目，我遇到了一些概念的麻烦，我试图谷歌周围无济于事！如何在MarsRoom类中实例化一定数量的加热器类加热器，然后在MasterControlPanel的主体中访问它们。但是取决于构造函数中设置的numheater的数量??我试过这个，但它没有认识到对象room1.roomheaters [0]。然而，如果我只是实例化像加热器roomheaters = new Heaters（）;这样的一个对象，它确实会认出它。非常感谢

public class MasterControlPanel{

    public static void main(String[] args){

    MarsRoom room1 = new MarsRoom(40, 40, 20, 20, 8, 2, 4);
    MarsRoom room2 = new MarsRoom(40, 40, 20, 20, 8, 2, 4);
    MarsRoom room3 = new MarsRoom(40, 40, 20, 20, 8, 2, 4);
    MarsRoom room4 = new MarsRoom(40, 40, 20, 20, 8, 2, 4);
    room1.createheaters();

    System.out.println("Turned " + (room1.roomheaters[0].getHeater() ? " ON" : " OFF"));
    }
}


public class MarsRoom extends Rooms implements RoomInterface{

int roomareasq;
int heatloss;
float insideTemp;
float outsideTemp;
float uvalue;
int numheaters;
int numlights;
Heaters roomheaters[] = new Heaters[numheaters];

public MarsRoom(){
}

public MarsRoom(int windowsH, int windowsW, int wallsH, int wallsW, int windowC, int heaters, int lights){
    windowsHeight = windowsH;
    windowsWidth = windowsW;
    wallsHeight = wallsH;
    wallsWidth = wallsW;
    windowCeiling = windowC;
    numheaters = heaters;
    numlights = lights; 
}

public void createheaters(){
for (int i=0; i < numheaters; i++)
{
roomheaters[i] = new Heaters();
}
}


public void calculateheatloss(){

}

}

Answer 1

数组roomheaters永远不会被声明，所以不可能填充它，更不用说从另一个类作为MarsRoom的属性访问它了：

roomheaters[i] = new Heaters();
// variables must be declared to be assigned

查看declaring member variables^Oracle

<强>更新

要将变量作为对象属性（如room1.roomheaters[0]）进行访问，它必须是成员变量。您只创建了一个 local 变量，该变量在函数返回后立即消失。上面的链接应该有所帮助。

Answer 2

您必须将roomheaters的实例化移出函数和类变量，并创建一个方法来访问加热器。在MarsRoom类中添加：

public Heaters[] getHeaters(){
  return roomheaters;
}

您可以致电room1.getHeaters()

来访问加热器

Java对象实例化

2 个答案: