File clean-up

data_structures/Lists/SinglyLinkedList.java

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+/**
+ * This class implements a SinglyLinked List. This is done
+ * using SinglyLinkedList class and a LinkForLinkedList Class.
+ * 
+ * A linked list is implar to an array, it hold values.
+ * However, links in a linked list do not have indexes. With
+ * a linked list you do not need to predetermine it's size as
+ * it gorws and shrinks as it is edited. This is an example of
+ * a singly linked list. Elements can only be added/removed
+ * at the head/front of the list.
+ * 
+ * @author Unknown
+ *
+ */
+class SinglyLinkedList{
+	/**Head refered to the front of the list */
+	private LinkForLinkedList head;
+
+	/**
+	 * Constructor of SinglyLinkedList
+	 */
+	public SinglyLinkedList(){
+		head = null;
+	}
+
+	/**
+	 * This method inserts an element at the head
+	 * 
+	 * @param x Element to be added
+	 */
+	public void insertHead(int x){
+		LinkForLinkedList newLink = new LinkForLinkedList(x); //Create a new link with a value attached to it
+		newLink.next = head; 		//Set the new link to point to the current head
+		head = newLink; 			//Now set the new link to be the head
+	}
+
+	/**
+	 * This method deletes an element at the head
+	 * 
+	 * @return The element deleted
+	 */
+	public LinkForLinkedList deleteHead(){
+		LinkForLinkedList temp = head;
+		head = head.next; //Make the second element in the list the new head, the Java garbage collector will later remove the old head
+		return temp;
+	}
+
+	/**
+	 * Checks if the list is empty
+	 * 
+	 * @return true is list is empty
+	 */
+	public boolean isEmpty(){
+		return(head == null);
+	}
+
+	/**
+	 * Prints contents of the list
+	 */
+	public void display(){
+		LinkForLinkedList current = head;
+		while(current!=null){
+			current.displayLink();
+			current = current.next;
+		}
+		System.out.println();
+	}
+	
+	/**
+	 * Main method
+	 * 
+	 * @param args Command line arguments
+	 */
+	public static void main(String args[]){
+		SinglyLinkedList myList = new SinglyLinkedList();
+
+		System.out.println(myList.isEmpty()); //Will print true
+
+		myList.insertHead(5);
+		myList.insertHead(7);
+		myList.insertHead(10);
+
+		myList.display(); // 10(head) --> 7 --> 5
+
+		myList.deleteHead();
+
+		myList.display(); // 7(head) --> 5
+	}
+}
+
+/**
+ * This class is the nodes of the SinglyLinked List.
+ * They consist of a vlue and a pointer to the node
+ * after them.
+ * 
+ * @author Unknown
+ *
+ */
+class LinkForLinkedList{
+	/** The value of the node */
+	public int value;
+	/** Point to the next node */
+	public LinkForLinkedList next; //This is what the link will point to
+
+	/**
+	 * Constructor
+	 * 
+	 * @param valuein Value to be put in the node
+	 */
+	public LinkForLinkedList(int valuein){
+		value = valuein;
+	}
+
+	/**
+	 * Prints out the value of the node
+	 */
+	public void displayLink(){
+		System.out.print(value+" ");
+	}
+
+}