AbstractQueue.java

import java.util.*;
 
public abstract class AbstractQueue extends AbstractCollection implements Queue
{
  protected AbstractQueue()
  {}
 
  public abstract Object dequeue();
 
  public abstract Object enqueue(Object object);
 
  public boolean equals(Object object)
  {
    if(object==this) 
      return true; 
    if(!(object instanceof AbstractQueue)) 
      return false; 
    AbstractQueue aq=(AbstractQueue) object; 
    if(aq.size()!=this.size()) 
      return false; 
    return containsAll(aq); 
  }
 
  public abstract Object getBack();
 
  public abstract Object getFront();
 
  public int hashCode()
  {
    int n=0;
    for(Iterator it=iterator(); it.hasNext(); )
    {
      Object object=it.next();
      if(object!=null)
        n+=object.hashCode();
    }
    return n;
  }
 
  public abstract Iterator iterator();
 
  public abstract int size();
}