SimpleQueue.java- Java Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Queue.html

import java.util.Queue;

import java.util.NoSuchElementException;

//Class for a simple queue based on SimpleList

//The "front" of the queue should be the front of

//the list.

//READ THE DOCUMENTATION for the Queue interface for more information

//on how these methods should work and when exceptions should

//be thrown. This data structure does not allow adding null.

//DO NOT re-implement nodes in this class... remember how

//inheritance works in Java and make use of that!

class SimpleQueue extends SimpleList implements Queue {

public boolean add(T item) {

//O(1)

return false;

}

public boolean offer(T item) {

//O(1)

return false;

}

public T remove() {

//O(1)

return null;

}

public T poll() {

//O(1)

return null;

}

public T element() {

//O(1)

return null;

}

public T peek() {

//O(1)

return null;

}

//-------------------------------------------------------------

// Main Method For Your Testing -- Edit all you want

//-------------------------------------------------------------

public static void main(String[] args){

SimpleQueue nums = new SimpleQueue<>();

nums.offer(2);

nums.offer(3);

nums.offer(5);

if (nums.peek() == 2 && nums.size()==3){

System.out.println("Yay 1");

}

if (nums.poll() == 2 && nums.poll() == 3

&& nums.poll() == 5 && nums.poll() == null){

System.out.println("Yay 2");

}

}

}

Since our priority queue is built out of a linked list, youll need to implement an update() method which accepts an item and "updates" its place in the queue (i.e. update its priority). Lower priority items should be at the front of the queue (since well want to pick the shortest lines, not the longest lines in our grocery store).

import java.util.NoSuchElementException;

import java.util.Date; //for testing

//priority queue where the minimum item has the highest priority

class PriorityQueue> extends SimpleQueue {

//updates an item that's already in the queue

//NOTE: This should update the exact item in memory,

//not just any "equal" item (in other words, you

//should use == here and not .equals())

public void update(T item) {

//O(n)

//throws NoSuchElementException if item is not

//in the queue

}

//You may need to override some other methods from SimpleQueue!

//Restriction 1: all methods from SimpleQueue should still work

//(as in, if you add(), the value should be added, if you call

//size() it should return the correct value, etc.). However,

//remove/poll will remove the _minimum_ value from the queue;

//element/peek will return the _minimum_ value from the queue.

//Restriction 2: element() and peek() must still both be O(1)

//-------------------------------------------------------------

// Main Method For Your Testing -- Edit all you want

//-------------------------------------------------------------

public static void main(String[] args){

PriorityQueue values = new PriorityQueue<>();

Date[] dates = new Date[5];

for (int i=5; i>=1; i--){

dates[i-1] = new Date(86400000*i);

values.add(dates[i-1]);

}

for(Date d : values) {

System.out.println(d);

}

dates[3].setTime(0);

values.update(dates[3]);

System.out.println();

for(Date d : values) {

System.out.println(d);

}

if(values.peek().equals(dates[3])) {

System.out.println(" Yay 1");

}

}

}