Swap

import java.util.Arrays;

public class Swap {
    public static void main(String[] args) {
        int[] arr={1,2,3,4,5,6,7,8,9};
        reverse(arr);
//        swap(arr,0,1);
        System.out.println(Arrays.toString(arr));
    }
    static void swap(int[] arr,int a,int b){
        int temp=arr[a];
        arr[a]=arr[b];
        arr[b]=temp;
    }

    static void reverse(int[] arr) {
        int start=0;
        int end=arr.length-1;
        while(start<end){
            swap(arr,start,end);
            start++;
            end--;
        }
    }

}