Question

我正在尝试创建一个计算平均值的void方法，但我想将值从main方法传递给方法。这是我想要做的一个例子：

 public class Plant {

    int leaves;
    int age;
    int sumLeaves;
    double average;

    void averageLeaves() {

        sumLeaves = leaves + leaves; //here is where I need help
        average = (double) sumLeaves / 2;
        System.out.println("The average number of leaves is: " + average);

    }

    public static void main(String[] args) {

        Plant plantA = new Plant();
        plantA.leaves = 5;

        Plant plantB = new Plant();
        plantB.leaves = 3;

        averageLeaves();

    }

我遇到的问题是将多种植物的价值纳入方法中。我尝试过使用.get，循环，static以及许多其他内容，但还没有想到它。我想要的是plantA.leaves和plantB.leaves对方法的价值，以便找到它们的总和。

Answer 1

由于您在Plant类中定义了averageLeaves()，因此您必须实际从其中一个工厂实例调用方法。这是你应该怎么做的。

plantA.averageLeaves();

你在这里犯的一个重大错误是，

sumLeaves = leaves + leaves;

这实际上添加了特定（一个）植物实例的叶子，这是错误的。你必须实际传递差异实例中的叶子数。

使用getter＆amp; amp ;;这是一个更好的方法。 setter方法。将averageLeaves()方法设为静态也很有意义。这样您就不需要实例来调用该方法。

    public class Plant {

    int leaves;
    int age;
    //int sumLeaves;  you do not need them now, as the averageLeaves method is static
    //double average;

    static void averageLeaves (int leaves1, int leaves2) {

        int sumLeaves = leaves2 + leaves1;               //here is where I need help
        double average = (double) sumLeaves / 2;
        System.out.println("The average number of leaves is: " + average);
    }

    void setLeaves(int leaves){
        this.leaves = leaves;
    }

    int getLeaves(){
        return this.leaves;
    }
}

    public class Main {

    public static void main(String[] args) {

        Plant plantA = new Plant();
        plantA.setLeaves(5);

        Plant plantB = new Plant();
        plantB.setLeaves(3);

        Plant.averageLeaves(plantA.getLeaves(), plantB.getLeaves());
    }
}

Answer 2

你必须这样做：

public class Plant 
{
    int age;
    int sumLeaves;
    double average;

    void averageLeaves (int leaves) 
    {
        sumLeaves = leaves + leaves;               //here is where I need help
        average = (double) sumLeaves / 2;
        System.out.println("The average number of leaves is: " + average);
    }
}

public class Example
{ 
        public static void main(String[] args) 
        {
            Plant plantA = new Plant();
            plantA.leaves = 5;

            Plant plantB = new Plant();
            plantB.leaves = 3;

            plantA.averageLeaves(plantA.leaves);
            plantB.averageLeaves(plantB.leaves);
        }
}

看看你只需要声明要输入到方法中的变量（在括号内），当你使用你的方法时，你必须传递方法将使用的值（按声明的顺序）在方法）。

我希望它会对你有所帮助！

Answer 3

有点不清楚你的意思。植物本身的平均值是多少？这两种植物的平均值。我假设后者。然后，一种方法是将方法作为静态成员调用，并将叶子作为参数传递。

public class Plant {

    int leaves;

    static void averageLeaves (int leaves1, int leaves2) {
        int sumLeaves = leaves1 + leaves2;    //here is where I need help
        double average = (double) sumLeaves / 2;
        System.out.println("The average number of leaves is: " + average);
    }

    public static void main(String[] args) {

        Plant plantA = new Plant();
        plantA.leaves = 5;

        Plant plantB = new Plant();
        plantB.leaves = 3;

        Plant.averageLeaves(plantA.leaves, plantB.leaves);

}

Answer 4

这是一个简单版本，允许您传入可变数量的植物并计算它们的平均值。

public class Plant {
    private int leaves;

    public Plant(int leaves) {
        this.leaves = leaves;
    }

    public int getLeaves() {
        return this.leaves;
    }

    public static void main(String[] args) {
        PrintLeavesAverage(
            new Plant(5),
            new Plant(10),
            new Plant(15),
            new Plant(12)
        );
    }

    private static void PrintLeavesAverage(Plant... plants) {
        int totalLeaves = 0;
        for (Plant p : plants) {
            totalLeaves += p.getLeaves();
        }
        double average = (double)totalLeaves/plants.length;
        System.out.println("The average number of leaves is: " + average);
    }
}

...或者如果你想获得更多的爱好者，并想尝试一些较新的Java 8功能，你可以使用流来计算平均值，如下所示：

private static void PrintLeavesAverage(Plant... plants) {
    OptionalDouble average = Arrays.stream(plants).mapToInt(p -> p.leaves).average();

    if (average.isPresent()) {
        System.out.println("The average number of leaves is: " + average.getAsDouble());
    } else {
        System.out.println("No plants, no average");
    }
}

将对象值传递给方法

4 个答案: