JavaAlgorithms/DataStructures/Queues/GenericArrayListQueue.java
Abhinandan Padmakar Pandey 9b38ecdfa6
Fix typos #2352 (#2382)
2021-10-08 19:32:34 +03:00

84 lines
2.1 KiB
Java

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