<p>i have a server - client application that runs on java 1.3; i want to change to java 1.6 step by step, meaning first few clients, than rest of the clients and finally server...
i was wondering could you direct me to some common problems that can come along and what should i look after?</p>

Off the top of my head, look for the names
```
enum
```
and
```
assert
```
in fields and local variables... These words have become keywords in java 1.4 and 5. The java 6 compiler will mark them as compilation errors if it sees them.
Yuval =8-)