Java Examples - Reversing a Collection

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Problem Description:

How to reverse a collection ?

Solution:

Following example demonstratres how to reverse a collection with the help of listIterator() and Collection.reverse() methods of Collection and Listiterator class .

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;

class UtilDemo3 {
   public static void main(String[] args) {
      String[] coins = { "A", "B", "C", "D", "E" };
      List l = new ArrayList();
      for (int i = 0; i < coins.length; i++)
         l.add(coins[i]);
      ListIterator liter = l.listIterator();
      System.out.println("Before reversal");
      while (liter.hasNext())
         System.out.println(liter.next());
      Collections.reverse(l);
      liter = l.listIterator();
      System.out.println("After reversal");
      while (liter.hasNext())
         System.out.println(liter.next());
   }
}

Result:

The above code sample will produce the following result.

Before reversal
A
B
C
D
E
After reversal
E
D
C
B
A


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