title: Java Calendar: calculate start date and end date of the previous week
body: <p>What is most convenient and shortest way to get start and end dates of the previous week? 
  Example: today is 2011-10-12 (input data),but I want to get 2011-10-03 (Monday's date of previous week) and 2011-10-09 (Sunday's date of previous week).</p>