打印数组平均值和最高值

Question

我正在尝试调用getAverage和getHighest到我的驱动程序类，并将它们打印在屏幕上。然而，我一直得到垃圾值。你知道这个程序有什么问题吗?谢谢你

public class ArrayOperations
{
    public double getAverage(int[] array)
    {
        double total = 0;
        double average;
        for (int index = 0; index < array.length; index++)
            total += array[index];
        average = total / array.length;
        System.out.println("The average is: " + average);
        return average;
    }
    public int getHighest(int[] array)
    {
        String output = new String("");
        int highest = array[0];
        for(int i = 1; i < array.length; i++)
        {
            if (array[i] > highest)
                highest = array[i];
            System.out.println("The highest score=" + highest);
        }
        return highest;
    }
}

驱动类:

public class ArrayOperationDriver
{
    public static void main(String[] args)
    {
        int [] testScores = {80, 90, 58, 75, 85, 45, 68, 72, 95};
        ArrayOperations object = new ArrayOperations();
        System.out.println(object);
    }
}

Answer 1

你不能在任何地方调用这些方法。只做

System.out.println(object.getAverage(testScore));
System.out.println(object.getHighest(testScore));

在你的代码中，你只是打印对象，它给了你该对象的字符串表示。

Answer 2

选项1:

你得到的"垃圾"值是object所在的内存位置。而是调用以下方法:

System.out.println(object.getAverage(testScores));
System.out.println(object.getHighest(testScores));

我将在你的代码中添加一个修改，这样它就不会打印大量的"The highest value is:"

public int getHighest(int[] array) {
    String output = new String("");
    int highest = array[0];
    for(int i = 1; i < array.length; i++) {
        if (array[i] > highest)
            highest = array[i];
            //Removed from here
            //System.out.println("The highest score=" + highest);
    }
    //Moved to here
    System.out.println("The highest score=" + highest);
    return highest; 
}

选项2:

但是由于您已经在方法内部打印，我将它们更改为void并取消return语句。如下:

public class ArrayOperations {
    public void getAverage(int[] array) {
        double total = 0; 
        double average; 
        for (int index = 0; index < array.length; index++)
            total += array[index];
        average = total / array.length;
        System.out.println("The average is: " + average);
    }
    public void getHighest(int[] array) {
        String output = new String("");
        int highest = array[0];
        for(int i = 1; i < array.length; i++) {
            if (array[i] > highest)
                highest = array[i];
        }
        System.out.println("The highest score=" + highest);
    }
}

和这样调用方法:

public class ArrayOperationDriver {
    public static void main(String[] args) {
        int [] testScores = {80, 90, 58, 75, 85, 45, 68, 72, 95};
        ArrayOperations object = new ArrayOperations();
        object.getAverage(testScores);
        object.getHighest(testScores);
    }
}

我想这是一个更干净的方法。

选项3:

还有一个选择是，从你的方法中返回数字，但从它们内部删除sop调用。

public class ArrayOperations {
    public double getAverage(int[] array) {
        double total = 0; 
        double average; 
        for (int index = 0; index < array.length; index++)
            total += array[index];
        average = total / array.length;
        return average;
    }
    public int getHighest(int[] array) {
        String output = new String("");
        int highest = array[0];
        for(int i = 1; i < array.length; i++) {
            if (array[i] > highest)
                highest = array[i];
        }
        return highest; 
    }
}

并将它们放入main方法中:

public class ArrayOperationDriver {
    public static void main(String[] args) {
        int [] testScores = {80, 90, 58, 75, 85, 45, 68, 72, 95};
        ArrayOperations object = new ArrayOperations();
        System.out.println("Average number is: " + object.getAverage(testScores));
        System.out.println("Highest number is: " + object.getHighest(testScores));
    }
}

编辑

要打印数组testScores中的所有数字，您可以在一个简单的for循环或for-each循环中做到这一点，我使用了for-each，但是如果您想知道如何使用，您可以尝试使用for。

public class ArrayOperationDriver {
    public static void main(String[] args) {
        int [] testScores = {80, 90, 58, 75, 85, 45, 68, 72, 95};
        ArrayOperations object = new ArrayOperations();
        System.out.println("Average number is: " + object.getAverage(testScores));
        System.out.println("Highest number is: " + object.getHighest(testScores));
        System.out.print("The test scores are: ");
        for (int score : testScores) 
            System.out.print(score + " ");
        System.out.println("");
    }
}

Answer 3

您没有调用getAverage或getHighest。您只是打印ArrayOperations，它实际上调用ArrayOperations.toString()。因为没有重写它，所以得到的是默认实现，它打印类名及其默认的hashCode()实现。

最佳实践是从ArrayOperations '方法中删除打印，只返回结果。打印应该由调用者(驱动程序)类处理。这样，如果调用者想对结果做其他事情(例如，在网页中显示它，将它保存到数据库中，执行另一个计算)，它可以。

public class ArrayOperationDriver
{
    public static void main(String[] args)
    {
        int [] testScores = {80, 90, 58, 75, 85, 45, 68, 72, 95};
        ArrayOperations object = new ArrayOperations();
        System.out.println
            ("The average score is: " + object.getAverage(testScores));
        System.out.println
            ("The highest score is: " + object.getHighest(testScores));
    }
}