java - 使用java中的方法

Question

我编写了以下代码来满足程序要求:

Average of Three Write a program that reads three whole numbers and displays the average of the three numbers.

Input Notes: Three whole numbers (non-negative integers) are entered at the console.

Output Notes (Prompts and Labels): The program prompts for the three integers with these strings: "Enter the first integer.", "Enter the second integer.", "Enter the third integer.". The program then prints         The average of NUMBER1,  NUMBER2,  and NUMBER3  = AVG   where NUMBER1  is the first integer value entered and NUMBER2  and NUMBER3  the subsequent integers, and AVG  is the computed average value.

SPECIFICATION OF NAMES: Your application class should be called Average3:

我的源代码:

import java.util.Scanner;
public class Average3 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        int AVG, NUMBER1, NUMBER2, NUMBER3;
        System.out.println("Enter the first integer.");
        Scanner keyboard = new Scanner(System.in);
        NUMBER1 = keyboard.nextInt();
        System.out.println("Enter the second integer.");
        NUMBER2 = keyboard.nextInt();
        System.out.println("Enter the third integer.");
        NUMBER3 = keyboard.nextInt();
        AVG = (NUMBER1 + NUMBER2 + NUMBER3) / 3;
        System.out.println("The average of NUMBER1, NUMBER2, and NUMBER3 = " + AVG);

    }

}

我的程序编译得很好，但我知道我可以实现并调用具有关联方法的对象，但我很难从哪里开始我从概念上理解方法和对象，但不知道编写代码。有人有什么建议吗？

Answer 1

首先，我将创建一个类 InputData这将存储用户的输入:

class InputData {
    public int number1;
    public int number2;
    public int number3;
}

这本身就是一种有用的通用技术:将多个相关值收集到单个数据结构中。然后您可以重写您的 main方法使用此类而不是三个单独的int变量，或者您可以更进一步，向 InputData 添加一些行为类(class)。显然要添加的第一个行为是计算平均值:

class InputData {
    public int number1;
    public int number2;
    public int number3;

    public int average() {
        return (number1 + number2 + number3) / 3;
    }
}

有了这个，你可以重写你的 main如下:

public class Average3 {
    static class InputData {
        public int number1;
        public int number2;
        public int number3;

        public int average() {
            return (number1 + number2 + number3) / 3;
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        InputData input = new InputData();
        System.out.println("Enter the first integer.");
        Scanner keyboard = new Scanner(System.in);
        input.number1 = keyboard.nextInt();
        System.out.println("Enter the second integer.");
        input.number2 = keyboard.nextInt();
        System.out.println("Enter the third integer.");
        input.number3 = keyboard.nextInt();
        System.out.println("The average of NUMBER1, NUMBER2, and NUMBER3 = "
            + input.average());
    }
}

请注意，我已经创建了 InputData一个static inner class的Average3 。它也可能是同一文件中的单独的顶级类(只要它不是 public )或单独文件中的类。

对此的改进是使用数组而不是单独的 int InputData 中的字段类(class)。您的程序可能如下所示:

public class Average3 {
    static class InputData {
        public int[] numbers;

        InputData(int size) {
            numbers = new int[size];
        }

        public int average() {
            int sum = 0;
            for (int number : numbers) {
                sum += number;
            }
            return sum / numbers.length;
        }
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        String[] prompts = { "first", "second", "third" };
        InputData input = new InputData(3);
        Scanner keyboard = new Scanner(System.in);
        for (int i = 0; i < prompts.length; ++i) {
            System.out.println("Enter the " + prompts[i] + " integer.");
            input.numbers[i] = keyboard.nextInt();
        }
        System.out.println("The average of NUMBER1, NUMBER2, and NUMBER3 = "
            + input.average());
    }
}

这里我向 InputData 添加了一个构造函数初始化数组并给它一个参数来设置数组的大小。

然后，您可以引入其他改进，例如使输入值的数量动态化(使用 ArrayList<Integer> 而不是 int 数组)。但这超出了作业的具体要求。有些人(实际上很多人)倾向于自动进行这种概括。然而，Extreme Programming的拥护者会指出，通常最好保持简单:根据今天的需求而不是明天、下周或下个月的需求进行设计和编码。

换句话说，您不知道下一个任务会带来什么，因此无论您如何概括当前任务，都可能会浪费工作。