Question

JAVA:

You're given two classes List.java and Node.java. In your List class you're supposed to implement the methods toFront, print, and toBack. The Node class is used as a reference no edit necessary.

LIST:

public class List {

protected Node head, tail;

/**

* Initialize the list to empty. Both head and tail

* are null references in this case.

*/

public List() {

// TODO Auto-generated constructor stub

head = tail = null;

}

/**

* Add nodeToAdd to the front (head) of this list.

* @param nodeToAdd to the front of this list.

*/

public void toFront(Node nodeToAdd) {

}

/**

* Print all nodes from the list to System.out

*/

public void print( ) {

}

/**

* Add nodeToAdd to the back (tail) of this list.

* @param nodeToAdd node to add at the back (tail) of this list.

*/

public void toBack (Node nodeToAdd) {

}

}

NODE:

public class Node {

protected String contents; // the contents of this LLNode

protected Node next; // Reference to next LLNode in list.

/**

* The constructor -- The default constructor will

* build a node with a null reference for the string

* and a null reference for the next item in the list.

*/

public Node() {

this(null, null);

}

/**

* Initializes this linked list node to the string

* given and sets the next reference to null.

* @param contents The string to store in this LLNode

*/

public Node(String contents) {

this (contents, null);

}

/**

* Initializes this linked list node to the string and

* LLNode reference passed in.

* @param contents The string to store in this LLNode

* @param next The reference to the next item in the List.

*/

public Node(String contents, Node next) {

this.contents = contents;

this.next = next;

}

/**

* @return the contents of this linked list node.

*/

protected String getContents() {

return contents;

}

/**

* @param contents the string to store in this linked list node.

*/

protected void setContents(String contents) {

this.contents = contents;

}

/**

* @return the reference to the next item in the Linked List

*/

protected Node getNext() {

return next;

}

/**

* @param next the Node to set as the node to follow this item in the list.

*/

protected void setNext(Node next) {

this.next = next;

}

}

Answer 1

I have implemented toFront(),toBack() and print() methods in List as per the given description.
PLEASE FIND THE FOLLOWING CODE SCREENSHOT, OUTPUT, AND CODE.

ANY CLARIFICATIONS REQUIRED LEAVE A COMMENT

1.CODE SCREENSHOT :

2.OUTPUT :

3.CODE:

List.java

public class List {

protected Node head, tail;

/**

* Initialize the list to empty. Both head and tail

* are null references in this case.

*/

public List() {



head = tail = null;

}

/**

* Add nodeToAdd to the front (head) of this list.

* @param nodeToAdd to the front of this list.

*/

public void toFront(Node nodeToAdd) {
        if(head == null) {    
            //If list is empty, both head and tail will point to new node    
            head = nodeToAdd;    
            tail = nodeToAdd;    
        }    
        else {    
            //nodeToAdd will be added after head such that head will point by nodeToAdd    
            nodeToAdd.setNext(head);    
            //nodeToAdd will become new head of the list    
            head = nodeToAdd;    
        }    
}

/**

* Print all nodes from the list to System.out

*/

public void print( ) {
                Node current = head;    
            
        if(head == null) {    
            System.out.println("List is empty");    
            return;    
        }    
        System.out.println("Nodes of list: ");    
        while(current != null) {    
            //Prints each node by incrementing pointer    
            System.out.print(current.getContents());    
            current = current.getNext();
                        if(current!=null)
                                System.out.print(" , ");                        
        }    
        System.out.println(); 
}

/**

* Add nodeToAdd to the back (tail) of this list.

* @param nodeToAdd node to add at the back (tail) of this list.

*/

public void toBack (Node nodeToAdd) {
        //Checks if the list is empty    
        if(head == null) {    
            //If list is empty, both head and tail will point to new node    
            head = nodeToAdd;    
            tail = nodeToAdd;    
        }    
        else {    
            //newNode will be added after tail such that tail's next will point to newNode    
            tail.setNext(nodeToAdd);    
            //newNode will become new tail of the list    
            tail = nodeToAdd;    
        }    

}

}

Node.java

public class Node {

protected String contents; // the contents of this LLNode

protected Node next; // Reference to next LLNode in list.

/**

* The constructor -- The default constructor will

* build a node with a null reference for the string

* and a null reference for the next item in the list.

*/

public Node() {

this(null, null);

}

/**

* Initializes this linked list node to the string

* given and sets the next reference to null.

* @param contents The string to store in this LLNode

*/

public Node(String contents) {

this (contents, null);

}

/**

* Initializes this linked list node to the string and

* LLNode reference passed in.

* @param contents The string to store in this LLNode

* @param next The reference to the next item in the List.

*/

public Node(String contents, Node next) {

this.contents = contents;

this.next = next;

}

/**

* @return the contents of this linked list node.

*/

protected String getContents() {

return contents;

}

/**

* @param contents the string to store in this linked list node.

*/

protected void setContents(String contents) {

this.contents = contents;

}

/**

* @return the reference to the next item in the Linked List

*/

protected Node getNext() {

return next;

}

/**

* @param next the Node to set as the node to follow this item in the list.

*/

protected void setNext(Node next) {

this.next = next;

}

}

Main.java

public class Main{
        public static void main(String[] args) {    
            
        List lst= new List();    
            
        //Add nodes to the list   
                
        lst.toBack(new Node("Smith"));     //   Smith
        lst.toFront(new Node("John"));     // John , Smith 
        lst.toFront(new Node("Neo"));      // Neo , John , Smith
            lst.toBack(new Node("Andrewson")); // Neo , John , Smith , Andrewson
        
        //Displays the nodes present in the list    
        lst.print();    
                // Neo , John , Smith , Andrewson
    }    
}

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