Help for correct generics syntax

Question

I'm trying to write a generics version of an old non-generics program. But after a few hours trials in this afternoon, I still fails in compile.
Error message from javac is:
Library3.java:55: cannot find symbol
symbol  : constructor SoftReference(BookShelf,java.lang.ref.ReferenceQueue<BookShelfReference>)
location: class java.lang.ref.SoftReference<BookShelf>
    super(shelf, collectedQueue);
    ^
1 errorAnd below is the code:
/* Library3.java
* from Item 11, Java Pitfalls, M.Daconta et al
* John Wiley & Sons, 2000
* trying to adapt to Java Generics feature
* hiwa, 13 Aug. 2007
import java.util.Random;
import java.lang.ref.SoftReference;
import java.lang.ref.ReferenceQueue;
class TextPage
  char[] symbols = new char[300];
class Book
  String      name;
  TextPage    pages[] = new TextPage[100];
  public Book ()
    for (int i = 0; i < pages.length; i++)
      pages[i] = new TextPage();
class BookShelf
  String subject;
  Book[] books = new Book[100];
  public BookShelf (String subject)
    this.subject = subject;
    for (int i = 0; i < books.length; i++)
      books[i] = new Book();
    if (subject.equals("Sports"))
      books[0].name = "History of Ping Pong";
class BookShelfReference extends SoftReference<BookShelf>
  String subject;
  //?? what should be the correct syntax here?
  static ReferenceQueue<BookShelfReference> collectedQueue
    = new ReferenceQueue<BookShelfReference>();
  public BookShelfReference (BookShelf shelf)
    //?? and here?
    super(shelf, collectedQueue);
    this.subject = shelf.subject;
class GarbageMonitor extends Thread
  ReferenceQueue queue;
  public GarbageMonitor (ReferenceQueue queue)
    this.queue = queue;
  public void run ()
    while (true)
      try
        BookShelfReference shelfRef =
          (BookShelfReference) queue.remove(5000);
        System.out.println("Monitor: Shelf subject '" +
            shelfRef.subject + "' was collected.");
      catch (Exception e)
      {   break;  }
public class Library3
  public static void main (String args[])
    String subjects[] = { "Sports", "New Age", "Religion",
      "Sci-Fi", "Romance", "Do-it-yourself",
      "Cooking", "Gardening", "Travel",
      "Mystery", "Fantasy", "Computers",
      "Business", "Young readers", "JW Books" };
    GarbageMonitor monitor =
      new GarbageMonitor(BookShelfReference.collectedQueue);
    monitor.start();
    BookShelfReference[] shelves = new BookShelfReference[25];
    int checkIndex = 10 + getRandomIndex(15);
    for (int i = 0; i < shelves.length; i++)
      String subject = subjects[getRandomIndex(subjects.length)];
      System.out.println("Creating bookshelf: " + (i + 1) +
          ", subject: " + subject);
      // Keep track of shelves as SoftReference objects
      shelves[i] = new BookShelfReference(new BookShelf(subject));
      // at a random interval check to see where the last
      //  "Sports" shelf was
      if (i == checkIndex)
        System.out.println("Checking for Sports...");
        for (int j = i; j >= 0; j--)
          // get BookShelf reference from SoftReference
          BookShelf shelf = (BookShelf)shelves[j].get();
          if (shelf != null)
            if (shelf.subject.equals("Sports"))
              System.out.println();
              System.out.println("Shelf " + (j + 1) +
                  " is Sports");
              System.out.println("First book is: " +
                  shelf.books[0].name);
              System.out.println();
              break;
            else
              System.out.println("No match. " +
                  "Subject was: " + shelf.subject);
  private static Random rnd = new Random(System.currentTimeMillis());
  private static int getRandomIndex (int range)
    return ((Math.abs(rnd.nextInt())) % range);
}

Answer 1

About ten minutes after posting previous post, I found the correct syntax by chance:
The previous code
  static ReferenceQueue<BookShelfReference> collectedQueue
    = new ReferenceQueue<BookShelfReference>();should be:
  static ReferenceQueue<BookShelf> collectedQueue
    = new ReferenceQueue<BookShelf>();But I still don't understand why the content of the referencequeue is specified as a referent type, not a reference type.