You can use a unix timestamp in java wit the following code:
String TimeStamp = "1324716371";
Date time=new Date((long)TimeStamp*1000);
Now, timestamp doesn't have to be a string, however in many of your projects you may have the value in that format. In this case, we convert it to a long (integer is too small), and then multiply it by 1000 since Java uses milliseconds.