（基础九）对给定的数组进行反转

public class reverseArrNum {    public static void main(String[] args){        int[] arr = {1,2,3,4,5,6,7,8,9};        System.out.println("翻转前：");        printArr(arr);        reverseArr(arr);        System.out.println("\n" + "翻转后：");        printArr(arr);    }    public static void reverseArr(int[] arr){        for(int start = 0, end = arr.length - 1; start < end; start++,end--){            swap(arr,start,end);        }    }    public static void swap(int[] arr,int i,int j){        int tmp = arr[i];        arr[i] = arr[j];        arr[j] = tmp;    }    public static void printArr(int[] arr){        for(int i = 0; i < arr.length; i++){            System.out.print("a[" + i + "]" + "=" + arr[i] + " ");        }    }}