import java.util.Arrays;

public class ArrayPractice {
	public static void swapFirstHalfWithSecondHalf(int[] a) {
		for (int i = 0; i < a.length / 2; i ++) {
			int j = i + (a.length + 1) / 2;
			// swap element at index i with element at index j
			int temp = a[i];
			a[i] = a[j];
			a[j] = temp;
		}
	}
	
	public static void main(String[] args) {
		int[] a = {10, 20, 30, 40};
		System.out.println(Arrays.toString(a));
		swapFirstHalfWithSecondHalf(a);
		System.out.println(Arrays.toString(a));
		a = new int[]{10, 20, 30, 40, 50};
		System.out.println(Arrays.toString(a));
		swapFirstHalfWithSecondHalf(a);
		System.out.println(Arrays.toString(a));
		
//		int[] a = new int[4];
//		a[0] = 10;
//		a[1] = 20;
//		a[2] = 30;
//		a[3] = 40;
		
	}

}