linkedlist1.java

java编程代码

public class LinkedList1
{
    private Node1 head;

    public LinkedList1( )
    {
        head = null;
    }

    /**
     Adds a node at the start of the list with the specified data.
     The added node will be the first node in the list.
    */
    public void addToStart(String itemName, int itemCount)
    {
        head = new Node1(itemName, itemCount, head);
    }

    /**
     Removes the head node and returns true if the list contains at least
     one node. Returns false if the list is empty.
    */
    public boolean deleteHeadNode( )
    {
        if (head != null)
        {
            head = head.getLink( );
            return true;
        }
        else
            return false;
    }

    /**
     Returns the number of nodes in the list.
    */
    public int size( )
    {
        int count = 0;
        Node1 position = head;

        while (position != null)
        {
            count++;
            position = position.getLink( );
        }
        return count;
    }

    public boolean contains(String item)
    {
        return (find(item) != null);
    }

    /**
     Finds the first node containing the target item, and returns a
     reference to that node. If target is not in the list, null is returned.
    */
    private Node1 find(String target)
    {
        Node1 position = head;
        String itemAtPosition;
        while (position != null)
        {
            itemAtPosition = position.getItem( );
            if (itemAtPosition.equals(target))
                return position;
            position = position.getLink( );
        }
        return null; //target was not found
    }

    public void outputList( )
    {
        Node1 position = head;
        while (position != null)
        {
            System.out.println(position.getItem( ) + " "
                                       + position.getCount( ));
            position = position.getLink( );
        }
    }

    public boolean isEmpty( )
	{
	    return (head == null);
	}

	public void clear( )
	{
	    head = null;
	}

}