*
 * @author higa
 * @param <E> the element type
 */
public class SLinkedList<E> implements Cloneable, Externalizable {

    static final long serialVersionUID = 1L;

    private transient Entry header = new Entry(null, null, null);

    private transient int size = 0;

    /**
     * Creates an {@link SLinkedList}.
     */
    public SLinkedList() {
        header.next = header;
        header.previous = header;
    }

    /**
     * {@link Thread} for the timer.
     */
    protected Thread thread;

    /**
     * A list for managing {@link TimeoutTask}.
     */
    protected final SLinkedList<TimeoutTask> timeoutTaskList = new SLinkedList<>();

    private TimeoutManager() {
    }

    /**
     * Returns the instance for the singleton.
     *
     * @return the instance for the singleton
     */

import org.codelibs.core.io.SerializeUtil;
import org.junit.Test;

/**
 * @author higa
 */
public class SLinkedListTest {

    private final SLinkedList<String> list = new SLinkedList<String>();

    /**
     * @throws Exception
     */
    @Test
    public void testGetFirstEntry() throws Exception {
        assertThat(list.getFirstEntry(), is(nullValue()));