Drain pineapple, reserving juice. (There should be ¼ to ½ cup.)
In a large bowl combine pineapple tidbits, cranberries, apple, and walnuts.
Stir in 2 ½ cups sugar and the reserved pineapple juice. Taste and add an additional ½ cup sugar, if you like.
Cover and refrigerate at least 2 hours, stirring once or twice.
Serve topped with whipped cream.
