（基础九）对给定的数组进行反转

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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] + " ");
        }
    }
}