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Copy pathQueue.java
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137 lines (96 loc) · 2.83 KB
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package com.inbravo.ds.queue;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicInteger;
/**
*
* @author amit.dixit
*
*/
public final class Queue {
/* Array for local storage */
private final long[] storage;
/* Maximum size limit of queue */
private final int maxSize;
/* Numbers of item in queue */
private final AtomicInteger currentItemsCount = new AtomicInteger(0);
/* FORM: Front at Zero (0) and Rear at Minus One (-1) */
/* Front of queue */
private final AtomicInteger front = new AtomicInteger(0);
/* Rear of queue */
private final AtomicInteger rear = new AtomicInteger(-1);
public Queue(final int maxSize) {
/* Create array with given size of queue */
storage = new long[maxSize];
/* Set max size */
this.maxSize = maxSize;
}
/**
* Insert at REAR of queue
*
* @param value
*/
public final void insert(final long value) {
/* Insert only if Queue is not FULL */
if (!isFull()) {
/* Set the value next to rear */
storage[rear.incrementAndGet()] = value;
/* Increment the current items count */
currentItemsCount.incrementAndGet();
} else {
/* Throw error */
throw new RuntimeException("Queue is full");
}
}
/**
* Remove from FRONT of queue
*
* @return
*/
public final long remove() {
/* Remove only if Queue is not EMPTY */
if (!isEmpty()) {
/* Take value at front */
final long removedValue = storage[front.get()];
/* Decrement the current items count */
currentItemsCount.getAndDecrement();
/* Reset the current front value and increment */
storage[front.getAndIncrement()] = 0;
return removedValue;
} else {
/* Throw error */
throw new RuntimeException("Queue is empty");
}
}
public final long peekFront() {
/* Return value at current index */
return storage[front.get()];
}
public final boolean isFull() {
return (currentItemsCount.get() == maxSize);
}
public final boolean isEmpty() {
return (currentItemsCount.get() == 0);
}
@Override
public final String toString() {
return (Arrays.toString(storage));
}
public static final void main(final String... args) {
/* Create new queue */
final Queue queue = new Queue(10);
/* Check for full */
System.out.println("Queue is full ? " + queue.isFull());
/* Check for empty */
System.out.println("Queue is empty ? " + queue.isEmpty());
System.out.println("Before element insert : " + queue);
for (int i = 0; i < 10; i++) {
/* Insert items on queue */
queue.insert(i + 10);
}
System.out.println("After element insert : " + queue);
while (!queue.isEmpty()) {
System.out.println("Removed " + queue.remove());
}
System.out.println("After element remove : " + queue);
}
}