java.lang.IllegalArgumentException: Illegal pattern character 'o'

wanted to convert from string to java.util.Date. for the same purpose I used following code,

String timeStamp = "Mon Feb 14 18:15:39 IST 2011"; 
DateFormat formatter = new SimpleDateFormat("dow mon dd hh:mm:ss zzz yyyy"); 
Date ts = (Date)formatter.parse(timeStamp); 

String timeStamp = "Mon Feb 14 18:15:39 IST 2011"; 
DateFormat formatter = new SimpleDateFormat("dow mon dd hh:mm:ss zzz yyyy"); 
Date ts = (Date)formatter.parse(timeStamp);

The format given to SimpleDateFormat() is format of java.util.Date. When you convert util's Date to string it comes in this format('dow mon dd hh:mm:ss zzz yyyy'). But when I execute code, It gives me Exception. I Don't know what exactly I needed to do to get rid of this problem. I am posting the part of StackTrace of exception. If anybody knows the solution,

java.lang.IllegalArgumentException: Illegal pattern character 'o' at java.text.SimpleDateFormat.compile(SimpleDateFormat.java:769) at java.text.SimpleDateFormat.initialize(SimpleDateFormat.java:576) at java.text.SimpleDateFormat.(SimpleDateFormat.java:501) at java.text.SimpleDateFormat.(SimpleDateFormat.java:476) Thank you in advance.
 
 
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Try this instead:
DateFormat formatter = new SimpleDateFormat("EEE MMM dd hh:mm:ss zzz yyyy"); 

DateFormat formatter = new SimpleDateFormat("EEE MMM dd hh:mm:ss zzz yyyy"); 
E is used for "Day in Week" as text, M is the month name.