Question

我最近正在学习数组，而我一直在这个问题上受困。

我基本上必须要求用户输入将要进入数组的数字，并且必须打印出偶数百分比，并且必须按照以下格式打印所有偶数。

Even values are : 89,22,-8, 0

我的代码是这个

import java.util.*;

public class Change {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        System.out.println("How many numbers in the array?");
        int num = input.nextInt();
        int count=0;
        int count1=0;

        for (int i=1; i<=num; i++) {

            System.out.println("Enter an integer: ");
            count++;
            int integer= input.nextInt();
            if(integer%2==0) {

                int list[]=new int[integer];
                count1++;
            }
        }

        System.out.println("There were "+((double)count1/count)*100+" percent of even numbers.");
        System.out.println("Even values are "+Arrays.toString(list)+"");

    }
}

此代码最终显示一条错误消息，提示“列表”未初始化。

我知道，因为“列表”位于for循环内，所以系统无法意识到它已被初始化，但是我不知道如何让系统识别“列表”。

任何帮助或评论都将受到赞赏。：）

Answer 1

对，首先让问题分解成几个小部分，然后逐个解决。首先，我们需要使用用户输入来创建和初始化数组。我们首先需要指定数组的大小-您已完成此操作。

        Scanner input = new Scanner(System.in);

        System.out.println("How many numbers in the array?");
        int num = input.nextInt();
        int evenCount = 0;
        int[] list = new int[num]; //set array size to user input

接下来，我们需要使用用户输入的数字填充数组。

        for (int i=0; i < list.length; i++){
            System.out.println("Enter an integer: ");
            int integer= input.nextInt();
            list[i] = integer; //set array value at index to user input
        }

最后，我们需要遍历数组中的每个数字并确定它是否为偶数。然后将其打印出来。

        System.out.print("Evens: ");
        for (int integer : list) {
            if (integer % 2 == 0) { //check if even
                evenCount++; //increment even number count
                System.out.print(" " + integer); //print the even integers
            }
        }

然后，将偶数个数除以数组中的总数，得到偶数个百分比。

         System.out.println("Even count: " + evenCount);
         System.out.println("Percent even: " + (double)evenCount / list.length);

完整代码：

public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        System.out.println("How many numbers in the array?");
        int num = input.nextInt();
        int evenCount = 0;
        int[] list = new int[num];

        for (int i=0; i < list.length; i++){
            System.out.println("Enter an integer: ");
            int integer= input.nextInt();
            list[i] = integer;
        }

        System.out.print("Evens: ");
        for (int integer : list) {
            if (integer % 2 == 0) {
                evenCount++;
                System.out.print(integer + " "); //print the even integers
            }
        }

         System.out.println();
         System.out.println("Even count: " + evenCount);
         System.out.println("Percent even: " + (double)evenCount / list.length);
    }

Answer 2

package com.inlet.ifserver;

import java.util.*;

public class x {
    public static void main(String[] args) {


        Scanner input = new Scanner(System.in);

        System.out.println("How many numbers in the array?");
        int num = input.nextInt();
        int count1 = 0;

        Integer[] evens = new Integer[num];

        for (int i = 0; i < num; i++) {

            System.out.println("Enter an integer: ");
            int integer = input.nextInt();
            if (integer % 2 == 0)
                evens[count1++] = integer;

        }

        evens = Arrays.copyOfRange(evens, 0, count1);

        System.out.println("There were " + ((double) count1 / num) * 100 + " percent of even numbers.");
        System.out.println("Even values are " + Arrays.toString(evens) + "");


    }
}

打印数组中偶数的百分比，并打印出数组中的偶数

2 个答案: