Question

这可能很简单，但我只是不知道怎么做？

如何从类文件中重用它：

int randomNum = 5 + (int)(Math.random() * ((10 - 5) + 1));

然后使用在另一个类文件中获得的相同结果？

我的CityWall类（包含我想要使用的int的类。）

public class CityWalls extends Thing {

    int randomNum = 5 + (int)(Math.random() * ((10 - 5) + 1));

    public CityWalls(City c, int st, int av, Direction d) {
        super(c, st ,av ,d);

        int oddIncrement = 0;
        if (randomNum % 2 == 0)
        {
            oddIncrement = 1;
        }

        for (int i = 0; i < randomNum; i++) {
            new Wall(c, i+(7-randomNum/2), (7-randomNum/2), Direction.WEST);
            new Wall(c, i+(7-randomNum/2), (7+randomNum/2) - oddIncrement, Direction.EAST);
            new Wall(c, (7-randomNum/2), i+(7-randomNum/2), Direction.NORTH);
            new Wall(c, (7+randomNum/2)-oddIncrement, i+(7-randomNum/2), Direction.SOUTH);
        }
    }

    public int getRandomNum() {
        return randomNum;
    }
}

这是我的世界级（我想重用变量的类）。

public class World {

    public static void main (String[] args) {
        int height = 0, width = 0, top = 5, left = 5, thingCount = 20;
        World b = new World();
        Random rand = new Random();
        // int RandomNumber = rand.nextInt(9);

        CityWalls cw = new CityWalls(Gothenburg, 5 , 5, Direction.NORTH); 
        int RandomNumber = cw.getRandomNum();

        height = (int)(Math.random() * 0.5) + RandomNumber; // I want to use the variable here.
        width = (int)(Math.random() * 0.5) + RandomNumber; // And here to replace the RandomNumber. then it should be correct.

        City Gothenburg = new City(16,16);


        Thing[] things = ThingSpawnCity(Gothenburg, width, height, top, left, thingCount);
        RobotFinder terminator = new RobotFinder(Gothenburg, 7, 7, Direction.NORTH, 0);

        terminator.run();
    }

    public static Thing[] ThingSpawnCity(City Gothenburg, int width, int height, int top, int left, int objects){
        Thing things[] = new Thing[objects];
        int avenue = 0, street = 0;

        for (int i = 0; i < objects; i++){
            avenue = (int)(Math.random() * width) + left;
            street = (int)(Math.random() * height) + top;
            things[i] = new Thing(Gothenburg, street, avenue);
        }

        return things;
    }
}

Answer 1

您需要引用要使用的类的实例。您需要访问要在该类中使用的字段。 e.g。

class A {
    int randomNum = 5 + (int)(Math.random() * ((10 - 5) + 1));
}

class B {
    public void printNum(B b) {
        System.out.println("Random Num " + b.randomNum);
    }
}

public static void main(String... ignored) {
    A a = new A();
    B b = new B();
    b.printNum(a);
}

Answer 2

阅读encapsulation和getters and setters，您可以这样做：

int randomNum = 5 + (int)(Math.random() * ((10 - 5) + 1));
MySuperOtherClass other = new MySuperOtherClass();
other.setX(randomNum);
// now you can get it back with other.getX();

Answer 3

在课堂上为其添加一个getter并公开

public int getRandomNum() {
    return randomNum;
}

修改

包含随机数的类：

public class ClassHavingARandomNumner { int randomNum = 5 + (int)(Math.random() * ((10 - 5) + 1)); public int getRandomNum() { return randomNum; } }

另一个想要访问随机数的类

public class ClassWantingARandomNumber { public static void main(String[] args) { // create an instance of the class containing the random number ClassHavingARandomNumner c = new ClassHavingARandomNumner(); // call the getter method to retrieve the random number System.out.println(c.getRandomNum()); } }

编辑2

第一步

int randomNum = 5 + (int)(Math.random() * ((10 - 5) + 1));

在构造函数之外，make randomNumber是类CiytWalls的成员变量

其次，将吸气剂添加到CityWalls

然后在main中将构造函数调用的结果赋值给局部变量

CityWalls cw = new CityWalls(Gothenburg, 5 , 5, Direction.NORTH);

之后，您可以使用以下方法访问您创建的CityWalls对象的随机数：

int rn = cw.getRandomNumber();

Answer 4

您可以将成员变量 randomNum 作为类 CityWalls 的静态变量来实现。并将该变量用于 World 类。通过这样做，您将获得与 CityWalls 类中指定的值相同的值。但是你实际上想重用，或者我会说使用同名的变量＆amp;不希望为它分配内存或您认为它对您的案例有用的任何其他原因，那么您应该将 CityWalls 类扩展到 World < / em> 类。

希望这澄清了你的疑问。

从不同的类重用变量？

4 个答案: