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Question
Use a SinglyLinked List to implement a Queue
a. Define a Queue interface.
b. Define a LinkedQueue class (Node class)..
c. Define a Test class to test all methods
help me make a test class
first code
package LinkedQueue;
import linkedstack.Node;
public class SLinkedList<E> {
private Node <E> head = null;
private Node <E> tail = null;
private int size = 0;
public SLinkedList() {
head = null;
tail = null;
size = 0;
}
public int getSize() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public E getFirst() {
if(isEmpty()) {
return null;
}
return head.getElement();
}
public E getLast() {
if(isEmpty()) {
return null;
}
return tail.getElement();
}
public void addFirst(E e) {
Node<E> newest = new Node<>(e, null);
newest.setNext(head);
head = newest;
if(getSize()==0) {
tail = head;
}
size++;
}
public void addLast(E e) {
Node<E> newest = new Node<>(e, null);
if(isEmpty()) {
head = newest;
} else {
tail.setNext(newest);
}
tail = newest;
size++;
}
public E removeFirst() {
if (isEmpty()) {
return null;
}
E firstE = head.getElement();
head = head.getNext();
size--;
if(getSize()==0) {
tail = null;
}
return firstE;
}
public void display() {
if (isEmpty()) {
System.out.println("Singly linked list is empty.");
}
else {
Node<E> temp = head;
System.out.println("=============== begining of lists================");
do {
System.out.println( "element =" + temp.getElement());
temp = temp.getNext();
}while (temp != null);
System.out.println("============== Ending of lists=================");
}
}
}
Secound code
package LinkedQueue;
public class LinkedQueue<E> implements Queue<E> {
private SLinkedList<E> list = new SLinkedList<>();
public LinkedQueue ( ) {}
public int size( ) {
return list.getSize();
}
public boolean isEmpty( ) {
return list.isEmpty( );
}
public void enqueue (E element) {
list.addLast(element);
}
public E first() {
return list.getFirst( );
}
public E dequeue() {
return list.removeFirst( );
}
}
third code
package LinkedQueue;
public interface Queue<E> {
int size();
boolean isEmpty( );
void enqueue(E e);
E first( );
E dequeue();
}
Transcribed Image Text:1 package LinkedQueue;
3 public class Node<E> {
4
private E element;
private Node <E> next;
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public Node (E e, Node<E> n) {
element = e;
next = n;
}
public E getElement () {
return element;
}
public Node<E> getNext () {
}
}
public void setElement (E e) {
element = e;
}
return next;
public void setNext (Node<E> n) {
next = n;
}
Expert Solution
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Step 1: Program Approach
The code you've provided is a Java implementation of a queue using a singly-linked list. Here's a breakdown of the code:
Queueinterface: It defines the methods that a queue should have, includingenqueue,dequeue, andisEmpty.Nodeclass: This is a simple class representing a node in the singly-linked list. Each node holds an integer value (data) and a reference to the next node in the list (next).LinkedQueueclass: It implements theQueueinterface. This class maintains a reference to theheadandtailnodes of the linked list.enqueue(int data): Adds a new node with the specified data to the end of the queue. If the queue is empty, bothheadandtailare set to the new node.dequeue(): Removes and returns the data from the front of the queue. If the queue is empty, it returns -1. If the queue becomes empty after dequeue, bothheadandtailare set to null.isEmpty(): Checks if the queue is empty by inspecting theheadreference.
Mainclass: The test class demonstrates how to use theLinkedQueue. It creates an instance ofQueueusing theLinkedQueueclass, enqueues three elements, and then dequeues and prints them in the order they were added.
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