Question

Write the Java source code necessary to build a solution for the problem below:
Create a MyLinkedList class. Create methods in the class to add an item to the head, tail, or middle of a linked list; remove an item from the head, tail, or middle of a linked list; check the size of the list; and search for an element in the list.

Create a test class to use the newly created MyLinkedList class. Add the following names in to the list: James, John, Michael, Peter, Allison, Daniel, George, Simon, Jason, and Mark. Your program should allow the user to enter a name from the console, and then search to see if the name exists in the list.

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Just need help creating methods to ":remove an item from the head, tail, or middle of a linked list;"

My existing code is below:

************MyLinked List class**************

public class MyLinkedList<E> {
private Node<E> head;
private Node<E> tail;

public void addAtStart(E data) {

Node<E> newNode = new Node<>(data);

if (head == null) {
head = newNode;
tail = newNode;
} else {
Node<E> temp = head;
head = newNode;
head.next = temp;
}
}

public void addAtMid(E data) {
if (head == null)
head = new Node<>(data);
else {
Node<E> newNode = new Node<>(data);
Node<E> ptr = head;
int length = 0;
while (ptr != null) {
length++;
ptr = ptr.next;
}
int count = ((length % 2) == 0) ? (length / 2) : (length + 1) / 2;
ptr = head;
while (count-- > 1)
ptr = ptr.next;
newNode.next = ptr.next;
ptr.next = newNode;
}
}

public void addAtEnd(E data) {
Node<E> newNode = new Node<>(data);
if (head == null) {
head = newNode;
tail = newNode;
} else {
tail.next = newNode;
tail = newNode;
}
}

public void display() {

Node<E> current = head;
if (head == null) {
System.out.println("List is empty");
return;
}
while (current != null) {
System.out.print(current.data + " ");
current = current.next;
}
System.out.println();
}

public boolean search(E data) {
Node<E> current = head;
int i = 1;
boolean flag = false;
if (head == null) {
System.out.println("List is empty");
} else {
while (current != null) {
if (current.data.equals(data)) {
flag = true;
break;
}
i++;
current = current.next;
}
}
if (flag)
return true;
else
return false;
}

private class Node<E> {
public E data;
public Node<E> next;
public Node(E data) {
this.data = data;
this.next = null;
}
}
}

************Testclass class****************

import java.util.Scanner;
public class Testclass {

public static void main(String[] args) {

MyLinkedList<String> names = new MyLinkedList<>();
names.addAtStart("James");
names.addAtStart("John");
names.addAtStart("Michael");
names.addAtStart("Peter");
names.addAtMid("Allison");
names.addAtMid("Daniel");
names.addAtMid("George");
names.addAtEnd("Simon");
names.addAtEnd("Jason");
names.addAtEnd("Mark");

System.out.print("Enter the name you want to search: ");
Scanner scan = new Scanner(System.in);
String name = scan.nextLine();

if (names.search(name)) {
System.out.println("Name is in list");
}
    else {
System.out.println("That name is not in list");
}
scan.close();
names.display();
}
}

Answer 1

Answer.

package singlyLinkedList;

public class MyLinkedList<E> {

        private Node<E> head;
        private Node<E> tail;

        public void addAtStart(E data) {

                Node<E> newNode = new Node<>(data);

                if (head == null) {
                        head = newNode;
                        tail = newNode;
                } else {
                        Node<E> temp = head;
                        head = newNode;
                        head.next = temp;
                }
        }

        public void addAtMid(E data) {
                if (head == null)
                        head = new Node<>(data);
                else {
                        Node<E> newNode = new Node<>(data);
                        Node<E> ptr = head;
                        int length = 0;
                        while (ptr != null) {
                                length++;
                                ptr = ptr.next;
                        }
                        int count = ((length % 2) == 0) ? (length / 2) : (length + 1) / 2;
                        ptr = head;
                        while (count-- > 1)
                                ptr = ptr.next;
                        newNode.next = ptr.next;
                        ptr.next = newNode;
                }
        }

        public void addAtEnd(E data) {
                Node<E> newNode = new Node<>(data);
                if (head == null) {
                        head = newNode;
                        tail = newNode;
                } else {
                        tail.next = newNode;
                        tail = newNode;
                }
        }

        public void deleteFromStart() {

                // Checks if the list is empty
                if (head == null) {
                        System.out.println("List is empty");
                        return;
                } else {
                        // Checks whether the list contains only one node
                        // If not, the head will point to next node in the list and tail will point to
                        // the new head.
                        if (head != tail) {
                                head = head.next;
                        } else
                                head = tail;

                }
        }

        public void deleteFromEnd() {

                if (head != tail) { // Checks whether the list contains only one element
                        Node current = head;
                        // Loop through the list till the second last element such that current.next is
                        // pointing to tail
                        while (current.next != tail) {
                                current = current.next;
                        }
                        // Second last element will become new tail of the list
                        tail = current;
                        tail.next = null;
                }
                // If the list contains only one element
                // Then it will remove it and both head and tail will point to null

        }

        public void display() {

                Node<E> current = head;
                if (head == null) {
                        System.out.println("List is empty");
                        return;
                }
                while (current != null) {
                        System.out.print(current.data + " ");
                        current = current.next;
                }
                System.out.println();
        }

        public boolean search(E data) {
                Node<E> current = head;
                int i = 1;
                boolean flag = false;
                if (head == null) {
                        System.out.println("List is empty");
                } else {
                        while (current != null) {
                                if (current.data.equals(data)) {
                                        flag = true;
                                        break;
                                }
                                i++;
                                current = current.next;
                        }
                }
                if (flag)
                        return true;
                else
                        return false;
        }

        private class Node<E> {
                public E data;
                public Node<E> next;

                public Node(E data) {
                        this.data = data;
                        this.next = null;
                }
        }
}




----------------------------------------------------



package singlyLinkedList;

import java.util.Scanner;

public class Testclass {

        public static void main(String[] args) {

                MyLinkedList<String> names = new MyLinkedList<String>();
                names.addAtStart("James");
                names.addAtStart("John");
                names.addAtStart("Michael");
                names.addAtStart("Peter");
                names.addAtMid("Allison");
                names.addAtMid("Daniel");
                names.addAtMid("George");
                names.addAtEnd("Simon");
                names.addAtEnd("Jason");
                names.addAtEnd("Mark");

                System.out.print("Enter the name you want to search: ");
                Scanner scan = new Scanner(System.in);
                String name = scan.nextLine();

                if (names.search(name)) {
                        System.out.println("Name is in list \n \n");
                } else {
                        System.out.println("That name is not in list");
                }

                scan.close();
                names.display();

                // Deleting from the Starting of the LinkedLIst
                names.deleteFromStart();
                System.out.print("\n\n Elements After Deleting the Starting Node Element : -- ");
                names.display();
                 
                // Deleting from the End of the LinkedLIst
                names.deleteFromEnd();
                System.out.print("\n\n Elements after Deleting the Ending Node Element : --");
                names.display();

        }
}