84 lines
2.3 KiB
Java
84 lines
2.3 KiB
Java
package DataStructures.Queues;
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import java.util.ArrayList;
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/**
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* This class implements a GenericArrayListQueue.
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* <p>
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* A GenericArrayListQueue data structure functions the same as any specific-typed queue.
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* The GenericArrayListQueue holds elemets of types to-be-specified at runtime.
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* The elements that are added first are the first to be removed (FIFO)
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* New elements are added to the back/rear of the queue.
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*
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*/
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public class GenericArrayListQueue<T> {
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/**
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* The generic ArrayList for the queue
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* T is the generic element
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*/
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ArrayList<T> _queue = new ArrayList<T>();
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/**
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* Checks if the queue has elements (not empty)
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*
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* @return True if the queue has elements. False otherwise.
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*/
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private boolean hasElements() {
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return !_queue.isEmpty();
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}
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/**
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* Checks what's at the front of the queue
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*
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* @return If queue is not empty, element at the front of the queue. Otherwise, null
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*/
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public T peek() {
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T result = null;
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if(this.hasElements()) { result = _queue.get(0); }
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return result;
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}
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/**
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* Inserts an element of type T to the queue.
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*
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* @param element of type T to be added
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* @return True if the element was added successfully
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*/
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public boolean add(T element) {
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return _queue.add(element);
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}
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/**
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* Retrieve what's at the front of the queue
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*
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* @return If queue is not empty, element retrieved. Otherwise, null
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*/
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public T poll() {
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T result = null;
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if(this.hasElements()) { result = _queue.remove(0); }
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return result;
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}
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/**
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* Main method
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*
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* @param args Command line arguments
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*/
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public static void main(String[] args) {
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GenericArrayListQueue<Integer> queue = new GenericArrayListQueue<Integer>();
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System.out.println("Running...");
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assert queue.peek() == null;
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assert queue.poll() == null;
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assert queue.add(1) == true;
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assert queue.peek() == 1;
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assert queue.add(2) == true;
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assert queue.peek() == 1;
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assert queue.poll() == 1;
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assert queue.peek() == 2;
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assert queue.poll() == 2;
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assert queue.peek() == null;
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assert queue.poll() == null;
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System.out.println("Finished.");
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}
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}
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