Question

对不起伙计们，我会重申这个问题。我有一个包含12个元素的数组：

1.6, 2.1, 1.7, 3.9, 3.7, 3.9, 2.9, 4.3, 2.4, 3.7

我想获得此数组中的最大值。问题是如何从我的主类调用方法到我在驱动程序类中创建的对象？

//MAIN CLASS
import java.util.Scanner;
public class Rainfall
{
    private double total = 0;
    private double average;
    private double max;
    private double smallest;
    private double rain[];
    Scanner scan = new Scanner(System.in);

public Rainfall(double...rainfall)
{
 double[] rain = {1.6 , 2.1, 1.7, 3.9, 3.7, 3.9, 2.9, 4.3, 2.4, 3.7};
}


public double getTotal()
{
    total = 0;
    for(int i = 0; i < 12; i++)
{
        total = total + rain[i];
}
    System.out.println("The total rainfall for the year is: " + total);

    return total;
}

public double getAverage()
{
    average = total/12;

    System.out.println("The average monthly rainfall is: " + average);

    return average;
}

public double getMostRain()
{

    double max = 0;
    int maxind = 0;

    for(int i = 0; i < 12; i++)
    {
        if (rain[i] > max)
        {
            max = rain[i];
            maxind = i;
        }
    }

System.out.println("The largest amout of rainfall was: " + max +
        "inches in month" + (maxind + 1));

return max;
}

public double getLeastRain()
{
    double smallest = Double.MAX_VALUE;
    int smallind = 0;

for(int n = 0; n < 12; n++)
{
    if (rain[n] < smallest)
    {
        smallest = rain[n];
        smallind = n;
    }
}


System.out.println("The smallest amout of rainfall was" + smallest +
        "inches in month " + (smallind + 1));

return smallest;
}
}



//DriverClass

public class RainfallDriver {


public static void main(String[] args) {
    double[] list = {1.6 , 2.1, 1.7, 3.9, 3.7, 3.9, 2.9, 4.3, 2.4, 3.7};

    //Counts the total and average from the elements in the array
    double total = 0;
    double average =0;
    for (double element : list)
        total += element;
            average = total/12;






    System.out.println("Total: " + total);
    System.out.println("Smallest: " +rain.getLeastRain());     //How can I call the method?
    System.out.println("Largest: " + rain.getMostRain());      //How can I call the method?
    System.out.println("Average: " + average);
}

}

Answer 1

如果你可以使用Java 8，那么新的Lambda Expressions可以用一个很好的单行解决问题：

double max = Arrays.stream(rain).max().getAsDouble();

您需要调用尾随getAsDouble()方法的原因是因为max()方法返回OptionalDouble，因为Java需要一种方法来处理rain的可能性}数组可能为空。

同样，您的其他方法可以实现如下：

double min = Arrays.stream(rain).min().getAsDouble();
double average = Arrays.stream(rain).average().getAsDouble();

或在一起：

DoubleStream rainStream = Arrays.stream(rain);
double max = rainStream.max().getAsDouble();
double min = rainStream.min().getAsDouble();
double average = rainSteam.average().getAsDouble();

Answer 2

我不确定你问的是什么......但是这样的事情会找到rain数组的最大元素。

int largestNum = 0;
for ( int i = 0; i < 12; i++ ) 
{
     if ( rain [ i ] >= largestNum )
        {
            largestNum = rain[ i ];
        }            
}

Answer 3

我看到它的方式，你不太了解OOP是什么，以及如何使用它：

您正在编写一个名为Rainfall的类，并且您（正确地）声明其成员（属性）......但您没有初始化它们！您的构造函数声明一个 local 变量，其名称与您的某个类的属性相同，但不会在任何地方使用它。

如果我所看到的是正确的，那么你想要的是这样的：

public class Rainfall {
    private double[] rain;
    /*
      It is a good idea to make the attributes private, and then access them
      through methods (getters to get the values, setters to change the values)
    */
    // more attributes  here
    public Rainfall(double[] rain) {
        this.rain = rain; // THIS IS THE WAY how you initialize an attribute
    }
    public double getRain() {
        /*
           Remember what I said about getters? This is an example
         */
        return rain;
    }
    public void setRain(double[] rain) {
        /*
           Remember what I said about setters? This is an example
         */
        this.rain = rain;
    }
    // More code...
}

现在，如果你想在另一个类中使用这个数组，你可以这样写：

public class SomeOtherClass {
    // Some code
    public static void main(String[] args) {
        Rainfall rainfall = new Rainfall(); // Declare and instantiate the object
        double[] rain = rainfall.getRain(); // Retrieve the value of the attribute
        /*
          And now... how to get the max value? Here's an example
         */ 
        double maxVal = Double.NEGATIVE_INFINITY;
        for(double x : rain) {
            if(x > maxVal)
                maxVal = x;
        }
        // More code
    }
}

我真的建议你好好阅读The Java Tutorials。

如何将带元素的数组添加到方法中？

3 个答案: