A generic CircularArray class that can be efficiently rotated and is iterable.

CircularArray.java

/*
 * A generic CircularArray class that can be efficiently rotated and is 
 * iterable.
 */
import java.util.Iterator;

public class CircularArray implements Iterable<Object> {

  private Object[] a;
  private int r;

  public CircularArray(Object[] a) {
    this.a = a;
    this.r = 0;
  }
  
  public void rotate(int r) {
    this.r = this.r + r % a.length;
  }

  /*
   * How to implement a Java Iterable class: https://stackoverflow.com/questions/5849154/can-we-write-our-own-iterator-in-java
   */
  @Override
  public Iterator<Object> iterator() {
    Iterator<Object> it = new Iterator<Object>() {
      private int index = r > 0 ? a.length - r : Math.abs(r);
      @Override
      public boolean hasNext() {
        return index < (r > 0 ? a.length - r + a.length  : Math.abs(r) + a.length );
      }
      @Override
      public Object next() {
        return a[index++ % a.length];
      }
      @Override
      public void remove() {
        throw new UnsupportedOperationException();
      }
    };
    return it;
  }

  public static void main(String[] args) {
    Integer[] a = new Integer[]{0, 1, 2, 3, 4};
    CircularArray ca = new CircularArray(a);
    int r = Integer.parseInt(args[0]);
    // before
    for (Integer i : a) {
      System.out.print(i + " ");
    }
    System.out.println();
    // rotate
    ca.rotate(r);
    System.out.println(r);
    // after
    for (Object o : ca) {
      System.out.print(o + " ");
    }
    System.out.println();
  }
}

Works with both positive and negative rotation values.