Need help with a Java problem: Queue.java: import stdlib.*; import java.util.Ite
ID: 3846050 • Letter: N
Question
Need help with a Java problem:
Queue.java:
import stdlib.*;
import java.util.Iterator;
import java.util.NoSuchElementException;
public class Queue<T> implements Iterable<T> {
private int N; // number of elements on queue
private Node<T> first; // beginning of queue
private Node<T> last; // end of queue
// helper linked list class
private static class Node<T> {
public Node() { }
public T item;
public Node<T> next;
}
/**
* Create an empty queue.
*/
public Queue() {
first = null;
last = null;
N = 0;
}
/**
* Is the queue empty?
*/
public boolean isEmpty() {
return first == null;
}
/**
* Return the number of items in the queue.
*/
public int size() {
return N;
}
/**
* Return the item least recently added to the queue.
* @throws java.util.NoSuchElementException if queue is empty.
*/
public T peek() {
if (isEmpty()) throw new NoSuchElementException("Queue underflow");
return first.item;
}
/**
* Add the item to the queue.
*/
public void enqueue(T item) {
Node<T> oldlast = last;
last = new Node<>();
last.item = item;
last.next = null;
if (isEmpty()) first = last;
else oldlast.next = last;
N++;
}
/**
* Remove and return the item on the queue least recently added.
* @throws java.util.NoSuchElementException if queue is empty.
*/
public T dequeue() {
if (isEmpty()) throw new NoSuchElementException("Queue underflow");
T item = first.item;
first = first.next;
N--;
if (isEmpty()) last = null;
return item;
}
/**
* Return string representation.
*/
public String toString() {
StringBuilder s = new StringBuilder();
for (T item : this)
s.append(item + " ");
return s.toString();
}
// check internal invariants
private static <T> boolean check(Queue<T> that) {
int N = that.N;
Queue.Node<T> first = that.first;
Queue.Node<T> last = that.last;
if (N == 0) {
if (first != null) return false;
if (last != null) return false;
}
else if (N == 1) {
if (first == null || last == null) return false;
if (first != last) return false;
if (first.next != null) return false;
}
else {
if (first == last) return false;
if (first.next == null) return false;
if (last.next != null) return false;
// check internal consistency of instance variable N
int numberOfNodes = 0;
for (Queue.Node<T> x = first; x != null; x = x.next) {
numberOfNodes++;
}
if (numberOfNodes != N) return false;
// check internal consistency of instance variable last
Queue.Node<T> lastNode = first;
while (lastNode.next != null) {
lastNode = lastNode.next;
}
if (last != lastNode) return false;
}
return true;
}
/**
* Return an iterator that iterates over the items on the queue in FIFO order.
*/
public Iterator<T> iterator() {
return new ListIterator();
}
// an iterator, doesn't implement remove() since it's optional
private class ListIterator implements Iterator<T> {
private Node<T> current = first;
public boolean hasNext() { return current != null; }
public void remove() { throw new UnsupportedOperationException(); }
public T next() {
if (!hasNext()) throw new NoSuchElementException();
T item = current.item;
current = current.next;
return item;
}
}
public void toGraphviz(String filename) {
GraphvizBuilder gb = new GraphvizBuilder ();
toGraphviz (gb, null, first);
gb.toFile (filename, "rankdir="LR"");
}
private void toGraphviz (GraphvizBuilder gb, Node<T> prev, Node<T> n) {
if (n == null) { gb.addNullEdge (prev); return; }
gb.addLabeledNode (n, n.item.toString ());
if (prev != null) gb.addEdge (prev, n);
toGraphviz (gb, n, n.next);
}
/**
* A test client.
*/
public static void main(String[] args) {
StdIn.fromString ("to be or not to - be - - that - - - is");
Queue<String> q = new Queue<>();
int count = 0;
q.toGraphviz ("queue" + count + ".png"); count++;
while (!StdIn.isEmpty()) {
String item = StdIn.readString();
if (!item.equals("-")) q.enqueue(item);
else if (!q.isEmpty()) StdOut.print(q.dequeue() + " ");
q.toGraphviz ("queue" + count + ".png"); count++;
}
StdOut.println("(" + q.size() + " left on queue)");
}
}
TestFinalAnswer.java:
package finalanswer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;
import stdlib.StdIn;
import stdlib.StdOut;
public class TestFinalAnswer {
public static <Item extends Comparable<? super Item>> boolean isSorted(Item[] a) {
for (int i = 0; i < a.length-1; i++) {
if (a[i].compareTo(a[i+1]) > 0) return false;
}
return true;
}
public static void main(String[] args) {
StdOut.println("*** " + FinalAnswer.yourName() + " ***");
StdOut.println();
Integer[] array = new Integer[12];
Random r = new Random();
for (int i = 0; i < array.length; i++) {
array[i] = r.nextInt(1000);
}
StdOut.println("Array before sorting: " + Arrays.toString(array));
FinalAnswer.minpqSort(array);
StdOut.println("Array after sorting: " + Arrays.toString(array));
StdOut.println("Array is sorted: " + isSorted(array));
StdOut.println();
Queue<String> queue = new Queue<String>();
queue.enqueue("first");
queue.enqueue("second");
queue.enqueue("third");
queue.enqueue("fourth");
StdOut.println("Queue before reversing: " + queue);
FinalAnswer.reverseQueue(queue);
StdOut.println("Queue after reversing: " + queue);
StdOut.println();
double[] frequencies = {110.0, 110.0*1.224, 110.0*1.224*1.224};
ArrayList<Chord> risingChords = FinalAnswer.createRisingChordList(0.2, frequencies, 10);
for (Chord risingChord: risingChords) {
StdOut.println("Playing: " + risingChord);
risingChord.play();
}
StdOut.println();
ArrayList<CTATrain> ctaTrains = new ArrayList<CTATrain>();
StdIn.fromFile("data/CTAdata.txt");
while (!StdIn.isEmpty()) {
int runNumber = StdIn.readInt();
String lineColor = StdIn.readString();
String nextStation = StdIn.readString();
String arrivalTime = StdIn.readString();
ctaTrains.add(new CTATrain(runNumber, lineColor, nextStation, arrivalTime));
}
StdOut.println("--- Trains before sorting ---");
for (CTATrain ctaTrain: ctaTrains) {
StdOut.println(ctaTrain);
}
StdOut.println();
ctaTrains.sort(null);
StdOut.println("--- Trains after sorting by run number ---");
for (CTATrain ctaTrain: ctaTrains) {
StdOut.println(ctaTrain);
}
StdOut.println();
ctaTrains.sort((CTATrain t1, CTATrain t2) -> (t1.getArrivalTime().compareTo(t2.getArrivalTime())));
StdOut.println("--- Trains after sorting by arrival time ---");
for (CTATrain ctaTrain: ctaTrains) {
StdOut.println(ctaTrain);
}
StdOut.println();
StdOut.println("=== " + FinalAnswer.yourName() + " ===");
}
}
Instructions 1. Eclipse, create a package called finalanswer. Copy and place into the package the file TestFinalAnswer.java provided below n the package, create a class called FinalAnswer. All of the static methods you are asked to write will go in this classExplanation / Answer
Answered as per question :-
package finalanswer;
import java.util.Stack;
public class FinalAnswer {
public static <T> Queue<T>reverseQueue(Queue<T> queue){
Stack<T> stack = new Stack<T>();
while(!queue.isEmpty()){
stack.push(queue.dequeue());
}
while(!stack.isEmpty()){
queue.enqueue(stack.pop());
}
return queue;
}
}
====================
Test and let me know if there is any concern.
Thanks