How to generate class diagrams and sequence diagrams from existing code?

[Bellrewqasa]

I have a Java code which I need to generate the class diagrams and sequence diagrams. I am using netbeans, but the code is 100% pure hand coded. How can I generate the class diagrams and sequence diagrams for existing code using netbeans?The code is separated into packages, so I need to generate class diagrams package wise. Which means, for an example, diagram 1 for package 1, diagram 2 for package 2 etc. Finally I need to take the generated GUI as an image.Please help!