数组倒转+求平均数——Java

• 思路：以length/2为界限，左右对应位置上的数字交换

package mulArray;

import java.util.Arrays;


public class arrayReverse {

    public static void main(String[] args) {
        int[] arr = new int[7];
        int len = arr.length;
        for (int i  = 0; i < len; ++i) {
            arr[i] = (int) (Math.random() * 100);
        }
        System.out.println(Arrays.toString(arr));

        // 翻转
        int index = len / 2; // (奇偶都一样)
        for (int i = 0; i < index; ++i) {
            int tmp = arr[i];
            arr[i] = arr[len - 1 -i];
            arr[len - 1 -i] = tmp;
        }
        System.out.println(Arrays.toString(arr));
    }
}

package mulArray;

import java.util.Arrays;
import java.util.Scanner;

public class avg {
    public static void main(String[] args) {
        int[] arr = new int[6];

        int index = 0;// 下标索引
        Scanner scan = new Scanner(System.in);
        while (true) {
            arr[index] = scan.nextInt();
            // 输入-1截止输入
            if (arr[index] < 0) {
                break;
            }

            if (++index >= arr.length) {
                // 下标越界，则扩容
                // 重新赋值索引
                arr = Arrays.copyOf(arr, arr.length + 5);
            }
        }

        // 求平均数
        double sum = 0;
        int cnt = 0;
        for (int i = 0; i < arr.length; ++i){
            if (arr[i] < 0) {
                break;
            }
            sum += arr[i];
            cnt++;
        }
        if (cnt == 0) System.out.println("error");
        else System.out.println("平均数" + sum/cnt);
        double avg = sum/cnt;
        // 输出比平均数大的数字
        for (int i = 0; i < cnt; ++i) {
            if (arr[i] > avg) {
                System.out.print(arr[i] + "t");
            }
        }


    }

}