emptybookmarks.java

书籍"Java_面向事件编程"的附带光盘代码

// Class used to store a list of bookmarks
class EmptyBookmarks {
    
    // returns true since this class only represents
    // empty lists
    public boolean isempty()
    {
        return true;
    }
        
    public EmptyBookmarks add(Bookmark entry)
    {
        return new NonemptyBookmarks( this, entry);
    }
        
    public Bookmark getSelectedItem( int position ) {
        throw new IllegalArgumentException("Index "+position+" is out of range");
    }

    public int getSize(  ) {
        return 0;
    }

}