CommonIterator.js

class MyIter implements Iterator {
  private Iter a;
  private Iter b;
  private Integer common;
  
  public MyIter(Iter a, Iter b) {
    if (a == null || b == null) {
      throw new Exceptin("Null");
    }

    this.a = a;
    this.b = b;
    this.common = null;
  }
  
  public Integer next() {
    if (!hasNext()) {
      throw new Exceptin();
    }
    Integer res = this.common;
    this.common = null;
    return res;
  }

  public boolean hasNext() {
    if (this.common != null) {
      return true;
    }

    Integer aa = this.getNext(this.a);
    Integer bb = this.getNext(this.b);
    
    if (aa == null || bb == null) {
      return false;
    }
    
    while (!aa.equals(bb)) {
      if (aa < bb) {
        aa = this.getNext(this.a);
      } else {
        bb = this.getNext(this.b);
      }
      if (aa == null || bb == null) {
        return false;
      }
    }
    
    this.common = aa;
    return true;
  }

  private Integer getNext(Iterator e) {
    if (e.hasNext()) {
      return e.next();
    }
    return null;
  }
}