OnJava8-Examples/onjava/CountingIntegerList.java

// onjava/CountingIntegerList.java
// List of any length, containing sample data.
package onjava;
import java.util.*;

public class CountingIntegerList
extends AbstractList<Integer> {
  private int size;
  public CountingIntegerList(int size) {
    this.size = size < 0 ? 0 : size;
  }
  @Override
  public Integer get(int index) {
    return index;
  }
  @Override
  public int size() { return size; }
  public static void main(String[] args) {
    System.out.println(new CountingIntegerList(30));
  }
}
/* Output:
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]
*/