Java which queue

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Angular 7. Machine Learning. Data Structures. Operating System. Computer Network. Or you can take approach with aggreagation by creating PureQueue with only one field which is type LinkedList object, list, and the only methods will be a default constructor, a copy constructor, isEmpty , size , add E element , remove , and element.

All those methods should be one-liners, as for example:. LinkedList implements that interface as mentioned above , but for your use, an ArrayDeque may be better -- you won't incur the cost of constant object allocations for each node. Then again, it may not matter which implementation you use.

Normal polymoprhism goodness comes to play: the beauty of writing against the Deque interface, rather than any specific implementation of it, is that you can very easily switch implementations to test which one performs best. Just change the line with new in it, and the rest of the code stays the same. ArrayDeque is likely to be faster than Stack interface while Stack is thread-safe when used as a stack, and faster than LinkedList when used as a queue.

If you know the upper bound of possible quantity of items in the queue, circular buffer is faster than LinkedList, as LinkedList creates an object link for each item in the queue. However, if you still want to use the recursive algorithm, you can change it to be "tail-recursive" which probably is optimized in the JVM to avoid stack overflows. Here is the Queue Implementation with Iterator and Iterable interface.

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Ask Question. Asked 9 years, 4 months ago. Active 6 days ago. Viewed k times. Improve this question. Pika Chu 57 6 6 bronze badges.

Georges Oates Larsen Georges Oates Larsen 6, 11 11 gold badges 46 46 silver badges 64 64 bronze badges. Maybe you need to step back and think about if there is a better way than pushing thousands of individual pixels one by one into a data structure if that is indeed what you are doing. It's a blob detection algorithm, the idea is that it starts from a point on the blob and traverses outwards to the edge of the blob.

I do not believe there is any other simple way of doing this. Also, the queue just stores points of interest -- It doesn't actually keep the pixels in the queue, the queue mainly just serves as a way of keeping track of where it is. Similar to many pathfinding algorithms — Georges Oates Larsen. The Queue interface does not define the blocking queue methods , which are common in concurrent programming. These methods, which wait for elements to appear or for space to become available, are defined in the BlockingQueue interface, which extends this interface.

Queue implementations generally do not allow insertion of null elements, although some implementations, such as LinkedList , do not prohibit insertion of null. Even in the implementations that permit it, null should not be inserted into a Queue , as null is also used as a special return value by the poll method to indicate that the queue contains no elements.

Queue implementations generally do not define element-based versions of methods equals and hashCode but instead inherit the identity based versions from class Object , because element-based equality is not always well-defined for queues with the same elements but different ordering properties. This interface is a member of the Java Collections Framework.

Since: 1. E element Retrieves, but does not remove, the head of this queue. E peek Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty.

E poll Retrieves and removes the head of this queue, or returns null if this queue is empty. E remove Retrieves and removes the head of this queue. Methods inherited from interface java. Collection addAll , clear , contains , containsAll , equals , hashCode , isEmpty , iterator , remove , removeAll , retainAll , size , toArray , toArray Method Detail add boolean add E e Inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions, returning true upon success and throwing an IllegalStateException if no space is currently available.

When using a capacity-restricted queue, this method is generally preferable to add E , which can fail to insert an element only by throwing an exception. Parameters: e - the element to add Returns: true if the element was added to this queue, else false Throws: ClassCastException - if the class of the specified element prevents it from being added to this queue NullPointerException - if the specified element is null and this queue does not permit null elements IllegalArgumentException - if some property of this element prevents it from being added to this queue remove E remove Retrieves and removes the head of this queue.