Package ptolemy.actor.util

Class FIFOQueue

  • All Implemented Interfaces:
    java.lang.Cloneable
    Direct Known Subclasses:
    FIFOQueueTest
    public class FIFOQueue
extends java.lang.Object
implements java.lang.Cloneable
    A first-in, first-out (FIFO) queue with variable capacity and optional history. Objects are appended to the queue with the put() method, and removed from the queue with the take() method. The object removed is the oldest one in the queue. By default, the capacity is infinite, but it can be set to any nonnegative size. If the history capacity is greater than zero (or infinite, by setting the capacity to INFINITE_CAPACITY), then objects removed from the queue are transferred to a history queue rather than simply removed. By default, the history capacity is zero.
    Since:
    Ptolemy II 0.2
    Version:
    $Id$
    Author:
    Edward A. Lee, Xiaojun Liu
    Pt.AcceptedRating:
    Green (liuj)
    Pt.ProposedRating:
    Green (eal)

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static int INFINITE_CAPACITY
      Used to indicate that the size of the queue or the history queue is infinite.

    • Constructor Summary

      Constructors 
      Constructor Description
      FIFOQueue()
      Construct an empty queue with no container.
      FIFOQueue​(FIFOQueue model)
      Copy constructor.
      FIFOQueue​(Nameable container)
      Construct an empty queue with the specified container.

    • Method Summary

      All Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      void clear()
      Remove all items currently stored in the queue and clear the history queue.
      java.lang.Object clone()
      Clone this queue.
      java.util.List elementList()
      List the objects in the queue, beginning with the oldest.
      java.util.Enumeration elements()
      Deprecated.
      Used elementList() instead.
      java.lang.Object get​(int offset)
      Return an object in the queue or history.
      int getCapacity()
      Return the queue capacity, or INFINITE_CAPACITY if it is unbounded.
      Nameable getContainer()
      Return the container of the queue, or null if there is none.
      int getHistoryCapacity()
      Return the capacity of the history queue.
      java.util.List historyElementList()
      List the objects in the history, which are the N most recent objects taken from the queue, beginning with the oldest, where N is less than or equal to the history capacity.
      java.util.Enumeration historyElements()
      Deprecated.
      Use historyElementList() instead.
      int historySize()
      Return the number of objects in the history.
      boolean isFull()
      Return true if the number of objects in the queue equals the queue capacity.
      boolean put​(java.lang.Object element)
      Put an object in the queue and return true if this will not cause the capacity to be exceeded.
      void setCapacity​(int capacity)
      Set queue capacity.
      void setContainer​(Nameable container)
      Set the container of the queue.
      void setHistoryCapacity​(int capacity)
      Set the capacity of the history queue.
      int size()
      Return the number of objects in the queue.
      java.lang.Object take()
      Remove the oldest object from the queue and return it.

      • Methods inherited from class java.lang.Object

        equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • INFINITE_CAPACITY

        public static final int INFINITE_CAPACITY
        Used to indicate that the size of the queue or the history queue is infinite.
        See Also:
        Constant Field Values

    • Constructor Detail

      • FIFOQueue

        public FIFOQueue()
        Construct an empty queue with no container.

      • FIFOQueue

        public FIFOQueue​(Nameable container)
        Construct an empty queue with the specified container. The container is only used for error reporting.
        Parameters:
        container - The container of the queue.

      • FIFOQueue

        public FIFOQueue​(FIFOQueue model)
        Copy constructor. Create a copy of the specified queue, but with no container. This is useful to permit enumerations over a queue while the queue continues to be modified. The objects in the queue themselves are not cloned.
        Parameters:
        model - The queue to be copied.

    • Method Detail

      • clear

        public void clear()
        Remove all items currently stored in the queue and clear the history queue. The queue capacity, history capacity and container remain unchanged.

      • clone

        public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException
        Clone this queue. The cloned queue has no container. The objects in the queue themselves are not cloned.
        Overrides:
        clone in class java.lang.Object
        Returns:
        A clone of this queue.
        Throws:
        java.lang.CloneNotSupportedException - If thrown by object.clone().F

      • elementList

        public java.util.List elementList()
        List the objects in the queue, beginning with the oldest.
        Returns:
        A list of objects.

      • elements

        @Deprecated
public java.util.Enumeration elements()
        Deprecated.
        Used elementList() instead.
        Enumerate the objects in the queue, beginning with the oldest. This method is deprecated and calls elementList()
        Returns:
        An enumeration of objects.

      • get

        public java.lang.Object get​(int offset)
                     throws java.util.NoSuchElementException
        Return an object in the queue or history. The object is not removed from the queue or history. If the offset argument is zero, return the oldest object in the queue. If the offset is 1, return the second oldest object, etc. If there is no such object in the queue (the offset is greater than or equal to the current queue size), throw an exception. If the argument is -1, return the most recent object that was put in the history. If the argument is -2, return the second most recent object in the history, etc. If there is no such object in the history (the history capacity is zero or the absolute value of the offset is greater than the current size of the history queue), throw an exception.
        Parameters:
        offset - The position of the desired object.
        Returns:
        The desired object in the queue or history.
        Throws:
        java.util.NoSuchElementException - If the offset is out of range.

      • getCapacity

        public int getCapacity()
        Return the queue capacity, or INFINITE_CAPACITY if it is unbounded.
        Returns:
        The capacity of the queue.
        See Also:
        setCapacity(int)

      • getHistoryCapacity

        public int getHistoryCapacity()
        Return the capacity of the history queue. This will be zero if the history mechanism is disabled and INFINITE_CAPACITY if the history capacity is infinite.
        Returns:
        The capacity of the history queue.
        See Also:
        setHistoryCapacity(int)

      • historyElementList

        public java.util.List historyElementList()
        List the objects in the history, which are the N most recent objects taken from the queue, beginning with the oldest, where N is less than or equal to the history capacity. If the history capacity is infinite, then the list includes all objects previously taken from the queue. If the history capacity is zero, then return an empty list.
        Returns:
        A list of objects in the history.

      • historyElements

        @Deprecated
public java.util.Enumeration historyElements()
        Deprecated.
        Use historyElementList() instead.
        Enumerate the objects in the history, which are the N most recent objects taken from the queue, beginning with the oldest, where N is less than or equal to the history capacity. This method is deprecated and calls historyElementList().
        Returns:
        An enumeration of objects in the history.

      • historySize

        public int historySize()
        Return the number of objects in the history.
        Returns:
        The current number of objects in the history.

      • isFull

        public boolean isFull()
        Return true if the number of objects in the queue equals the queue capacity.
        Returns:
        A boolean indicating whether the queue is full.

      • put

        public boolean put​(java.lang.Object element)
        Put an object in the queue and return true if this will not cause the capacity to be exceeded. Otherwise, do not put the object in the queue and return false.
        Parameters:
        element - An object to be put in the queue.
        Returns:
        A boolean indicating success.

      • setCapacity

        public void setCapacity​(int capacity)
                 throws IllegalActionException
        Set queue capacity. Use INFINITE_CAPACITY to indicate unbounded capacity (which is the default). If the current size of the queue exceeds the desired capacity, throw an exception.
        Parameters:
        capacity - The desired capacity.
        Throws:
        IllegalActionException - If the queue contains more objects than the proposed capacity or the proposed capacity is illegal.
        See Also:
        getCapacity()

      • setContainer

        public void setContainer​(Nameable container)
        Set the container of the queue. The container is only used for error reporting.
        Parameters:
        container - The container of this queue.
        See Also:
        getContainer()

      • setHistoryCapacity

        public void setHistoryCapacity​(int capacity)
                        throws IllegalActionException
        Set the capacity of the history queue. Use 0 to disable the history mechanism and INFINITE_CAPACITY to make the history capacity unbounded. If the size of the history queue exceeds the desired capacity, remove the oldest objects from the history queue until its size equals the proposed capacity. Note that this can be used to clear the history queue by supplying 0 as the argument.
        Parameters:
        capacity - The desired capacity of the history queue.
        Throws:
        IllegalActionException - If the desired capacity is illegal.
        See Also:
        getHistoryCapacity()

      • size

        public int size()
        Return the number of objects in the queue.
        Returns:
        The number of objects in the queue.

      • take

        public java.lang.Object take()
                      throws java.util.NoSuchElementException
        Remove the oldest object from the queue and return it. If there is no such object in the queue (the queue is empty), throw an exception. If the history mechanism is enabled, then put the taken object in the history queue. If the capacity of the history queue would be exceeded by this, then first remove the oldest object in the history queue.
        Returns:
        An object from the queue.
        Throws:
        java.util.NoSuchElementException - If the queue is empty.