java学习p188

import java.util.Scanner;
public class a1 {
    public static void main(String[] args) {
        Scanner myScanner = new Scanner(System.in);
        System.out.println("请输入数组的元素个数");
        int length = myScanner.nextInt();
        int[] arr = new int[length];                    //另一种方法(arr[i]已赋值)
        double sum = 0;                                 //double sum = arr[0];
        int max = 0;                                    //int max = arr[0];
        int maxIndex = 0;                               //int maxIndex = 0;
        for (int i = 0; i < arr.length; i++) {          //for (int i = 1; i < arr.length; i++) {
            arr[i] = (int)(Math.random() * 100) + 1;    //    sum += arr[i];
            sum += arr[i];                              //    if(max < arr[i]) {
            if (max < arr[i]) {                         //       max = arr[i];
                max = arr[i];                           //       maxIndex = i;
                maxIndex = i;                           //    }
            }                                           //}
        }
        System.out.println("=====正序输出=====");
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println("n" + "=====倒序输出=====");
        for (int i = arr.length - 1; i >= 0; i--) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
        System.out.println("平均值为 " + (sum / arr.length) + "n"
                + "最大值为 " + max + "n" + "最大值下标为 " + maxIndex);
        System.out.println("请输入要查找的数");
        int[] indexArr = new int[0];
        int count = 0, mark = 0;
        int findNum = myScanner.nextInt();
        for (int i = 0; i < arr.length; i++) {
            if (arr[i] == findNum) {
                count++;
            }
            if (count != mark) {//记录要查找的数的下标
                int[] newIndexArr = new int[indexArr.length + 1];
                if (indexArr.length == 0) {
                    newIndexArr[0] = i;
                }
                else {
                    for (int j = 0; j < indexArr.length; j++) {
                        newIndexArr[j] = indexArr[j];
                    }
                    newIndexArr[newIndexArr.length - 1] = i;
                }
                indexArr = newIndexArr;
            }
            mark = count;
        }
        if (count == 0) {
            System.out.println("没有找到" + findNum);
        }
        else {
            System.out.print("找到了" + count + "个" + findNum + ",下标为 ");
            for (int i = 0; i < indexArr.length; i++) {
                if (i == indexArr.length - 1) {
                    System.out.print(indexArr[i]);
                }
                else {
                    System.out.print(indexArr[i] + ", ");
                }
            }
        }
    }
}