使用swing做的熟悉控件使用的DEMO

				package book;				import java.util.HashSet;				import java.util.Iterator;				import java.util.Collection;				import java.util.ArrayList;				import userexception.*;								/**				* class BookList				*/				public class BookList {					private static BookList instance = new BookList();					private HashSet books = null;					private int booknum;										//constructor					private BookList() {						booknum = 1;						books = new HashSet();						try {							addBook(new Book(booknum++, "Ten Years", "Kit", Book.COMPUTER, 30.00, "China"));							addBook(new Book(booknum++, "Red And Black", "Unknown", Book.COMPUTER, 30.00, "People"));							addBook(new Book(booknum++, "C Programming", "Kit", Book.COMPUTER, 30.00, "China"));							addBook(new Book(booknum++, "Three Pigs", "Tom", Book.NONCOMPUTER, 34.00, "Family"));						} catch (AddException e) {													}										}									//static methods to get the instance					public static BookList getInstance() {						return instance;					}											//get the books					public HashSet getBooks() {						return books;					}										//add a book					public void addBook(Book bk) throws AddException {						if(! books.add(bk)) throw new AddException();					}									//find books 					public Collection query(String name, String author, int cat, String from) throws BookNotFoundException{						ArrayList result = new ArrayList();						Book tmpBook = null;						Iterator i = books.iterator();						while (i.hasNext()) {							tmpBook = (Book)i.next();							if(!name.equals("")) {								if(! tmpBook.getName().equals(name)) continue;								} 							if(!author.equals("")) {								if(! tmpBook.getAuthor().equals(author)) continue;							}							if(!(cat < 0)) {								if(! (tmpBook.getBookType() == cat)) continue;							}							if(!from.equals("")) {								if(! tmpBook.getFrom().equals(from)) continue;							}							System.out.println(tmpBook);							result.add(tmpBook);						}										if(result.size() == 0) throw new BookNotFoundException();						return result;					}									//unique search by bookid					public Book queryById (int bookid) throws BookNotFoundException {						Iterator i = books.iterator();						Book temp = null;						while (i.hasNext()) {							temp = (Book)i.next();							if(temp.getBookId() == bookid) {								break;							}							}						if(temp == null) throw new BookNotFoundException();						return temp;					}										//modify a book					public void modifyBook(Book bk) throws BookNotFoundException {						Book old = queryById(bk.getBookId());						/*							if( old != null) {							books.remove(old);							books.add(bk);						}						*/						old.setName(bk.getName());						old.setAuthor(bk.getAuthor());						old.setBookType(bk.getBookType());						old.setCost(bk.getCost());						old.setFrom(bk.getFrom());											}										//make unique number for the new book					public int makeNo() {						return booknum++; 					}				}