Reverse an integer array !!

Problem statement:  Reverse an integer array in java !
Using  for Loop:

1. public class ReverseNumberArray {
2. public static void main(String[] args) {
3. int a[] = { 2, 4, 6, 7, 3, 56, 34 };
4. for (int i = 0; i < a.length / 2; i++) {
5. int temp = a[i];
6. a[i] = a[a.length - 1 - i];
7. a[a.length - 1 - i] = temp;
8. }
9. for (int i : a) {
10. System.out.print(i + " ");
11. }
12. }
13. }

Output: 

34 56 3 7 6 4 2 

Time complexity: O(n/2)

Using while Loop:

1. public class ReverseNumberArray {
2. 
   
3. public static void main(String[] args) {
4. int a[] = { 2, 4, 6, 7, 3, 56, 34 };
5. 
   
6. int end = a.length - 1;
7. int start = 0;
8. Object temp;
9. while (start < end) {
10. temp = a[start];
11. a[start] = a[end];
12. a[end] = (int) temp;
13. start++;
14. end--;
15. }
16. for (int i : a) {
17. System.out.print(i + " ");
18. }
19. }
20. }

Output: 

34 56 3 7 6 4 2 

Time complexity: O(n/2)

Using Java 8 Stream API:

1. import java.util.stream.IntStream;
2. 
   
3. public class ReverseArrayUsingStream {
4. public static void main(String[] args) {
5. Integer a[] = { 2, 4, 6, 7, 3, 56, 34 };
6. reverseUsingStream(a);
7. }
8. 
   
9. static void reverseUsingStream(Object a[]) {
10. 
    
11. Object rev[] = IntStream.rangeClosed(1, a.length).mapToObj(i -> a[a.length - i]).toArray();
12. for (Object s : rev) {
13. System.out.print(s + " ");
14. }
15. }
16. }

Using Collections.reverse():

1. import java.util.List;
2. import java.util.Arrays;
3. import java.util.Collections;
4. 
   
5. public class ReverseArrayCollections {
6. public static void main(String[] args) {
7. 
   
8. Object a[] = { 2, 4, 6, 7, 3, 56, 34 };
9. reverseUsingCollectionsUtils(a);
10. }
11. static void reverseUsingCollectionsUtils(Object[] array) {
12. List<Object> list = Arrays.asList(array);
13. Collections.reverse(list);
14. for (Object i : list) {
15. System.out.print(i + " ");
16. }
17. }
18. }

Output:
34 56 3 7 6 4 2