Java Collection: PriorityQueue

• Extends AbstractQueue and implements the Queue interface
• Prioritized by the queue's comparator
• Dynamic: can grow

class PriorityQueue

• Can accept custom constructors
• Otherwise use default constructor -- sort the queue in ascending (从小到大) order

• offer() -- adding element to queue
• poll() -- removing element from queue

public class Main {
    public static void main(String[] args) {
        Queue q = new PriorityQueue<>();
        // 添加3个元素到队列:
        q.offer("apple");
        q.offer("pear");
        q.offer("banana");
        System.out.println(q.poll()); // apple
        System.out.println(q.poll()); // banana
        System.out.println(q.poll()); // pear
        System.out.println(q.poll()); // null,因为队列为空
    }
}