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Thread: Best way of implementing a queue's isEmpty() method

  1. #1
    Junior Member pyler's Avatar
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    Default Best way of implementing a queue's isEmpty() method

    You have a queue called someQ
    There are two ways to find out if the queue is empty()
    head == null;
    size()  == 0;
    size == 0;

    where size() is determined by the number of elements enqueued onto the queue by incrementing a global variable called

    Which is the best method and why?
    Last edited by pyler; April 6th, 2014 at 10:28 PM.

  2. #2
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    Default Re: Best way of implementing a queue's isEmpty() method

    You have some Queue<E> someQ = new Queue<E>()
    invalid syntax, Queue is an interface so you cannot use the new key word in java to make a new object of it.

    if you are determining the size, then use the size() method.
    comparing head == null is an alternative since peek, peekFirst method returns a null when the array is empty, but I think that is not 100% accurate. why?

    what if I have a Queue of String generic. and I pushed these values:
    the top of stack in Queue is null so if you are determining if the Queue is empty using head == null, then you can conclude that the above Queue is empty, but actually not, it returns a null just because its top of stack is null, but actually it has 3 elements.

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