bookmarklist.java

书籍"Java_面向事件编程"的附带光盘代码

import java.io.*;

// class to handle a list of bookmarks
// the bookmarks can be saved or loaded from an html formatted file
public class BookmarkList {

    private EmptyBookmarks list;  // the list of bookmarks

    public BookmarkList( ){
        list = new EmptyBookmarks();
    }

    // return the number of bookmarks in the list
    public int size( ){
        return list.getSize();
    }

    // return the bookmark at index 
    public Bookmark getSelectedItem( int index ){
        return list.getSelectedItem( size() - (index + 1) );
    }
    
    // add a bookmark to the list
    public void add( Bookmark entry ){
        list = list.add(entry);
    }
    
    // Print all bookmark entries
    public void printBookmarks()
    {
        for ( int i = 0; i < size(); i++) {
            System.out.println( getSelectedItem(i).toString() );
        }
    }
    
    //  Place all the bookmarks in the list into the bookmarks.html
    //  file.  Use the standard format employed by most common
    //  browsers.
    public void saveBookmarksFile() {
        
        try { 
            
            //  Access the file through a PrintWriter 
            PrintWriter bookmarksFile =
                new PrintWriter( new FileWriter("bookmarks.html")) ;
            
            //  place prologue in file
            bookmarksFile.println("<!DOCTYPE NETSCAPE-Bookmark-file-1>");
            bookmarksFile.println(
                                  "<!-- This is an automatically generated file.");
            bookmarksFile.println("It will be read and overwritten.");
            bookmarksFile.println("Do Not Edit! -->");
            bookmarksFile.println("<TITLE>Bookmarks</TITLE>");
            bookmarksFile.println("<H1>Bookmarks</H1>");
            bookmarksFile.println("");
            bookmarksFile.println("<DL><p>");
            
            //  add one <DL> line describing each bookmark
            for ( int i = 0; i < size(); i++)
                bookmarksFile.println( getSelectedItem(i).toBookmarkFileEntry());
            
            //  add epilogue and close file
            bookmarksFile.println("</DL><p>");
            bookmarksFile.close();
            
        } catch ( IOException e) {
            System.out.println("Unable to save bookmarks file - " + e.getMessage()); 
        }
    }
    
    
    //  Add all the bookmarks found in the file "bookmarks.html"
    //  to this list of Bookmarks.
    public void retrieveBookmarksFile() {
        
        try {
            BufferedReader bookmarksFileReader =
                new BufferedReader( new FileReader( "bookmarks.html" ));
            
            //  Read through all the lines of the file
            
            String curLine = bookmarksFileReader.readLine();
            while ( curLine != null ) {
                
                //  process lines that appear to contain bookmarks
                if ( curLine.indexOf( "<A ") >= 0 ) {
                    
                    Bookmark entry = extractBookmark( curLine );
                    if ( entry != null ){
                        add( entry );
                    }
                }
                
                //  move on to the next line
                curLine = bookmarksFileReader.readLine();
                
            }
            
            bookmarksFileReader.close();
            
        } catch ( IOException e) {
            System.out.println("Unable to retrieve bookmarks - " + e.getMessage());
        }
    }

    // extract the the description and address of a bookmark from a line of
    // html formatted text
    private Bookmark extractBookmark( String line ) {
        final String UrlPreSeq = "HREF=\"";
        final String UrlPostSeq = "\"";
        final String NamePreSeq = "\">";
        final String NamePostSeq = "</A>";
        
        String url, name;
        int start, end;
        
        start = line.indexOf( UrlPreSeq );
        end = line.indexOf( UrlPostSeq , start + UrlPreSeq.length());
        
        System.out.println(line+","+start+","+end);
        if ( end > 0 ) {
            url = line.substring( start + UrlPreSeq.length(), end );
            System.out.println( url );
            
            start = line.indexOf( NamePreSeq, end );
            end = line.indexOf( NamePostSeq, start + NamePreSeq.length() );
            
            if ( end > 0 ) {
                name = line.substring( start + NamePreSeq.length() , end );
                System.out.println( name );
                return new Bookmark( name, url );
            }
        }
        
        return null;
    }
        
    
}