The java.util.PriorityQueue
Priority queue
In computer science, a priority queue is an abstract data type which is like a regular queue or stack data structure, but where additionally each element has a "priority" associated with it. In a priority queue, an element with high priority is served before an element with low priority. If two elements have the same priority, they are served according to their order in the queue.
Why does JDK return null?
What is the difference between element and remove in Java 7?
What is an exception in a queue?
Why use exception throwing methods?
What are the three pillars of OOP?
Should you remove or prefer element?
See 3 more
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Difference between peek(), poll() and remove() method of Queue ...
This represents a collection that is indented to hold data before processing. It is an arrangement of the type First-In-First-Out (FIFO). The first element put in the queue is the first element taken out from it.
Difference between peek poll and remove method of the Queue interface ...
Peek() - It will give the head element of the queue. If queue is empty then it will return null. Poll() - It will give the head element of the queue and will remove ...
Differences between poll () and remove () methods of Queue Interface in ...
poll() vs remove() methods of Queue Interface in Java: Here, we are going to learn what are the differences between poll() and remove() method of Queue interface in Java programming language? Submitted by Preeti Jain, on August 05, 2019 . poll() vs remove() methods of Queue Interface . Here, we will see how poll() method differs from remove() method of Queue interface in Java?
Queue peek() method in Java - GeeksforGeeks
The peek() method of Queue Interface returns the element at the front the container. It does not deletes the element in the container. This method returns the head of the queue. The method does not throws an exception when the Queue is empty, it returns null instead.. Syntax:
Deque (Java Platform SE 7 ) - Oracle
Note that the peek method works equally well when a deque is used as a queue or a stack; in either case, elements are drawn from the beginning of the deque.. This interface provides two methods to remove interior elements, removeFirstOccurrence and removeLastOccurrence. Unlike the List interface, this interface does not provide support for indexed access to elements.
Why does JDK return null?
In many cases, the JDK frequently returns null on "failure" when null could never be a "positive" answer, and throws exceptions otherwise -- for example, NavigableMap.firstKey () can return null because null is the first key, so it throws a NoSuchElementException on an empty map, while NavigableMap.firstEntry () returns null on an empty map because there's no possibility of confusing null with a valid return.
What is the difference between element and remove in Java 7?
The only difference mentioned is that element () and remove () throws an exception for empty queue. We can manually throw an exception (in case we need that) if the queue is empty.
What is an exception in a queue?
The exception is the difference. If your Queue should have elements, use element () or remove (), so there's an exception if the Queue is empty. If it is reasonable that the Queue can be empty, use poll () and peek () and deal with the null value.
Why use exception throwing methods?
There is one semi-justified reason to include the exception-throwing methods: their existence allows a solution where a null is a legitimate item in the queue. Whenever you need such a scenario, without these methods you'd need to create a "null-sentinel" value that represents null; using the methods there is less boilerplate.
What are the three pillars of OOP?
As to whether this approach tallies with OOP principles - I don't think it's relevant. OOP's three pillars (polymorphism, inheritance and encapsulation) don't cover the inclusion of methods of dubious necessity. OOP isn't about solving efficiency & effectiveness issues.
Should you remove or prefer element?
In general, you should prefer element () or remove () if the queue should never be empty at this point in the program. That's part of the general principle of failing fast: if something is wrong, throw an error as soon as possible so it can be debugged. (If your program doesn't throw up as soon as a bug happens, then it gets significantly harder to trace that bug, because you only find out about it later on at a different place in the stack.)
Why does JDK return null?
In many cases, the JDK frequently returns null on "failure" when null could never be a "positive" answer, and throws exceptions otherwise -- for example, NavigableMap.firstKey () can return null because null is the first key, so it throws a NoSuchElementException on an empty map, while NavigableMap.firstEntry () returns null on an empty map because there's no possibility of confusing null with a valid return.
What is the difference between element and remove in Java 7?
The only difference mentioned is that element () and remove () throws an exception for empty queue. We can manually throw an exception (in case we need that) if the queue is empty.
What is an exception in a queue?
The exception is the difference. If your Queue should have elements, use element () or remove (), so there's an exception if the Queue is empty. If it is reasonable that the Queue can be empty, use poll () and peek () and deal with the null value.
Why use exception throwing methods?
There is one semi-justified reason to include the exception-throwing methods: their existence allows a solution where a null is a legitimate item in the queue. Whenever you need such a scenario, without these methods you'd need to create a "null-sentinel" value that represents null; using the methods there is less boilerplate.
What are the three pillars of OOP?
As to whether this approach tallies with OOP principles - I don't think it's relevant. OOP's three pillars (polymorphism, inheritance and encapsulation) don't cover the inclusion of methods of dubious necessity. OOP isn't about solving efficiency & effectiveness issues.
Should you remove or prefer element?
In general, you should prefer element () or remove () if the queue should never be empty at this point in the program. That's part of the general principle of failing fast: if something is wrong, throw an error as soon as possible so it can be debugged. (If your program doesn't throw up as soon as a bug happens, then it gets significantly harder to trace that bug, because you only find out about it later on at a different place in the stack.)
