QueueDL.java

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package aud;
 
import aud.adt.AbstractQueue;
import java.util.NoSuchElementException;
 
//@<queuedl:class
public class QueueDL<T> extends AbstractQueue<T> {
 
  DList<T> data_;
 
  public QueueDL() { data_=new DList<T>(); }
//@>queuedl:class
 
  //@<queuedl:state
  @Override public boolean is_empty() {
    return data_.empty();
  }
  @Override public T front() {
    if (data_.empty())
      throw new NoSuchElementException();
    return data_.front();
  }
  //@>queuedl:state
 
  //@<queuedl:manip
  @Override public T dequeue() {
    if (data_.empty())
      throw new NoSuchElementException();
    T obj=data_.front();
    data_.pop_front();
    return obj;
  }
 
  @Override public void enqueue(T x) {
    data_.push_back(x);
  }
  //@>queuedl:manip
 
  @Override public String toString() {
    if (is_empty())
      return "<";
 
    String s="";
    DList<T>.ForwardIterator i=data_.iterator();
    while (i.hasNext()) {
      s+=i.next().toString()+"<";
    }
    return s;
  }
}