One way to reduce cyclomatic complexity that I see is to replace the switch statement. Just create an array or HashMap that will map month index to number;
public void setFinalDateForProject(Integer year,Integer month, Integer weekId) {
String[] months = new String[] {"01", "02", "03", "04", "05", ...}
// Replace switch statement
String projectMonth = months[month];
// Rest of your code
...
}
Another way to solve this problem will be to replace mapping of numbers to strings with converting integer to String using String.format. Use something like:
String projectMonth = String.format("%02d", month + 1);