Arraylist & Reverse, an Array List in #Java
Java ArrayList class uses a dynamic Array for storing the elements.
Some important points of array list :
1 ] No Size Limit.
2] Flexible than Traditional Array
3] ArrayList in Java can have the duplicate elements also.
4] It implements the List interface.
5] The ArrayList maintains the insertion order internally.
6] Array List class maintains insertion order.
7] Array List allows random access because the array works on an index basis.
Let's come to the problem :
Our Arraylist :
List<Integer> noList = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
Expected Arraylist :
List<Integer> expectedList = new ArrayList<>(Arrays.asList(7, 6, 5, 4, 3, 2, 1));
Using Collections.reverse Method
List<Integer> noList = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7)); Collections.reverse(noList);
but in some case we dont want to change original array list so what will we do ?
we will take new object and store this array list in that and then will do reverse operation.
List<Integer> originalList = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
List<Integer> newList = new ArrayList<>(originalList); Collections.reverse(newList);
Second way to do reverse using recursion .
public class DemoReverseList {
public static <T> void reverseWithRecursion(List<T> list) {
if (list.size() > 1) {
T value = list.remove(0);
reverseWithRecursion(list);
System.out.println(value);
list.add(value);
}
}
public static void main(String[] args) {
List<Integer> List = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
DemoReverseList.reverseWithRecursion(List);
System.out.println(List);
}
}
Thanks for reading.
Keep sharing.
