SetLinked

package com.setLinked;
    /**
     * @author Lloyd Samuel Garcia
     * 04986 CC-DataStruc21
     *  3:00 PM - 5:30 PM TTH
     * MySetLinked - linked-list implementation of MySet interface
     */
import java.util.StringTokenizer;

public class MySetLinked implements MySet {

    private Node head, tail;
    public int cardinality;
    private Node position;

    // constructor
    public MySetLinked(Object[] items) {
        for (int i = 0; i < items.length; addElement(items[i]), i++);//editonun
    }

    //default constructor
    public MySetLinked() {

    }

    @Override
    public boolean isFull() { return false; }

    @Override
    public boolean isEmpty() { return cardinality == 0; }

    @Override
    public boolean isElement(Object item) {
        boolean found = false;
        if (!isEmpty()) {
            // sequential search
            Node tnode = head;
            while (tnode != null) {
                if (tnode.getItem().equals(item)) { found = true; position = tnode; break;}
                tnode = tnode.getNext();
            }
        }
        return found;
    }

    @Override
    public boolean addElement(Object item) {
        boolean isElem = !isElement(item);
        if (isElem) {
            Node node = new Node(item);
            if (!isEmpty())
                tail.setNext(node);
            else
                head = node;
            tail = node;
            cardinality++;
        }
        return isElem;
    }

    @Override
    public boolean deleteElement(Object item) {
        boolean isElem = isElement(item);
        Node tnode = head;
        if (head == position) {
            head = tnode.getNext();
            tnode = null;
        } else {
            Node tnodenext;
            for(tnodenext = tnode.getNext();tnodenext != position;tnode = tnode.getNext(),tnodenext = tnode.getNext()){
            }if (tnodenext == tail) {
                tail = tnode;
                tail.setNext(null);
            } else
                tnode.setNext(tnodenext.getNext());
            tnodenext = null;
        }
        cardinality--;
        return isElem;
    }

    @Override
    public MySet union(MySet parset) {
        MySet union = new MySetLinked();
        MySetLinked set = (MySetLinked) parset;
        Node node = head;
        while(node != null) {
            union.addElement(node.getItem());
            node = node.getNext();
        }
         StringTokenizer setTokens = new StringTokenizer(set.toString(), "{},");
         for(setTokens.hasMoreTokens(),union.addElement(setTokens.nextToken());;)

        return union;
    }

    @Override
    public MySet intersect(MySet parset) {
        MySet intersect = new MySetLinked();
        MySetLinked pset = (MySetLinked) parset;
        // populate the result set
        for (Node node = head; node != null; node = node.getNext()) {
            if (pset.isElement(node.getItem()))
                intersect.addElement(node.getItem());
        }
        return intersect;
    }

    @Override
    public MySet difference(MySet parset) {
        MySet difference = new MySetLinked();
        MySetLinked set = (MySetLinked) parset;
        for (Node node = head; node != null; node = node.getNext()) {
            if (!set.isElement(node.getItem()))
                difference.addElement(node.getItem());
        }
        return difference;
    }

    @Override
    public MySet crossproduct(MySet parset) {
        MySet crossproduct = new MySetLinked();
        MySetLinked set = (MySetLinked) parset;
        for (Node node = head; node != null; node = node.getNext()) {
            StringTokenizer setTokens = new StringTokenizer(set.toString(), "{},");
            while (setTokens.hasMoreTokens()) {
                MySetLinked temp = new MySetLinked();
                temp.addElement(node.getItem());
                temp.addElement(setTokens.nextToken());
                if (temp.cardinality == 2)
                    crossproduct.addElement(temp);
            }
        }
        return crossproduct;
    }

    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("{");
        for (Node node = head; node != null; node = node.getNext()) {
            sb.append(node.getItem());
            if (node.getNext() != null)
                sb.append(",");
        }
        sb.append("}");
        return sb.toString();
    }
}