Abstractqueue in Java

I. Overview of the CLASS structure:

Java.lang.Object  java.util.abstractcollection<e>      java.util.abstractqueue<e>

Type parameter:

E -The type declaration of the element saved in this collection: Public abstract class abstractqueue<e> extends Abstractcollection <E> implementsQueue <E>

This class provides a Queue backbone implementation of some operations. Implementations in this class apply when a basic implementation does not allow the inclusion of a null element. add, remove and element methods are based on offer , poll and methods, respectively, peek but they indicate failure by throwing an exception instead of returning false or null .

Extending the Queue implementation of this class must define at least one method that does not allow the insertion of a null element, and that method, Queue.offer(E) Queue.peek() Queue.poll() Collection.size() and both, and Collection.iterator() both support Iterator.remove() methods. It is also common to override other methods. If these requirements are not met, you can instead consider AbstractCollection creating a subclass.

This class is a member of the Java collections Framework.

second, the construction method

Abstractqueue ()  The construction method used by the subclass.

Iii. details of the method

1.Add(e e)

true illegalstateexception.

 Offer true illegalstateexception.

  
 

   
 
 
 
    
  
 
   
 
     specified by:  
   
 
   

     interface 
     collection<e>  add 
   
 
   
 
     specified by:  
   
 
   

     interface 
     queue<e>  
     Add  
   
 
   
 
     Overwrite:  
   
 
   

     class 
     abstractcollection<e>  
     Add  
   
 
     
  
    
   
   
 
  
  
 

   
 
 
 
    
  
 
   
 
     parameter:  
   
 
   
 
     e -element to add 
   
 
   
 
     return:  
   
 
   
  true  (according to 
     Collection.add (E) ) 
   
 
   
 
     thrown:   
   
 
   
 
     illegalstateexception -If the element cannot be added at this time because of capacity constraints 
   
 
   
 
     classcastexception -As The class of the specified element does not allow the element to be added to this queue 
   
 
   
 
     nullpointerexception -If the specified element is null and this queue does not allow null elements 
   
 
   
 
     illegalargumentexception -If some properties of this element do not allow the element to be added to this queue 
   
 
  
 2, 
    public  E 
      
     
   remove   
     ()  
   
 
  

   
   
  
 
    
   

     gets and removes the header for this queue. This method differs from 
     poll  in that it throws an exception when this queue is empty. 
    
 This implementation returns the result of  poll  unless the queue is empty. 
 
    
 
 
   
 
    
   
 
    
 
     
 
       specified by:  
     
 
     

       Interface 
       queue< ; E>  
       Remove  
     
 
    
 
   
 
    
   
 
    
 
     
 
       return:  
     
 
     

       header for this queue 
     
 
     
 
       thrown:  
     
 
     
 
       nosuchelementexcep tion -If this queue is empty 
     
 
    
 
   
 
   
  
 3, public e    element    () gets the header of this queue without removing it. This method differs from  Peek  in that it throws an exception when this queue is empty. This implementation returns the result of  peek  unless the queue is empty. 

   
   
  
 
    
   
 
    
 
      specified by:  
    
 
    

      interface 
      Queue<e>  in 
      element  
    
 
   
 
   
   
  
 
   
  
 
    
   
 
    
 
      return:  
    
 
    

      header for this queue 
    
 
    
 
      thrown:  
    
 
    
 
      nosuchelementexception -If this queue is empty 
    
 
   
 4, 
    public void  
     
    Clear   
     poll  until it returns  null . 
 
   
  

 
   
  

  
    
   Designated by:
 
   
  
 
   
  

   
  
    
   Collection<E> in the interface. 
  
    
   clear
 
   
  
 
   
  

  
    
   Covered:
 
   
  
 
   
  

   
  
    
   AbstractCollection<E> in the class 
  
    
   clear
 
   
  

5,addall(CollectionE> C)

illegalargumentexception. In addition, if the specified collection is modified while this operation is in progress, the behavior of this operation is indeterminate.

null Element), if a run-time exception is encountered, it may cause only certain elements to be added successfully when the associated exception is thrown.

  
 

   
 
 

 
    
  
 
   
 
    Designated by: 
   
 
   
 
    Collection<E>in the interface. 
    addAll 
   
 
   
 
    Covered: 
   
 
   
 
    AbstractCollection<E> in the 
    addAll class 
   
 
  
 

   
 
  
  
 

   
 
 

 
    
  
 
   
 
    Parameters: 
   
 
   
 
    c-The collection that contains the elements to add to this queue 
   
 
   
 
    Return: 
   
 
   

     Returns true if this queue has changed because of a call 
   
 
   
 
    Thrown: 
   
 
   
 
    ClassCastException -If the class that specifies the collection element does not allow the element to be added to this queue 
   
 
   
 
    NullPointerException -If the specified collection contains a null element and this queue does not allow a null element, or the specified co Llection is null 
   
 
   
 
    IllegalArgumentException -If certain properties of the specified collection element do not allow the element to be added to this queue, or collection is the queue 
   
 
   
 
    IllegalStateException -As All elements cannot be added at this time due to insertion limit 
   
 
  
 

   
 
  

Abstractqueue in Java