Well, I guess you could use an object depending on how the parameters are related to one another. I'm sure others can give better advice on that.
However, remember that as of JDK 1.5 you can use the 'varargs' feature to pass (almost) as many parameters as you like to a method and have them treated like an array. Of course, the parameters will have to be of the same type though.
There is not clearcut number for the max. number of arguments - only rules of thumb. I try to limit my methods to not more than 3 arguments (4 in rare cases). If you have too many arguments, you might be doing too many things in that method.
Remember the "Single Responsibility Principle". Each software artifact should do one, and only one job well.
I do tend to get a bit lenient on the private methods though (may be upto 6 parameters), especially if it reuses some piece of code and since they are not seen by other classes.
In general, if you see yourself using more than 3-4 arguments in a public method, consider defining a data structure (value object) that can be passed around or rethink your design to eliminate that need.