ipblock/java problems

ipblock (part of iplist and similar to moblock) wasn't working for me and the problem appears to have been with java. To fix it, I did the following:
1. First, make sure sun java, rather than openjdk, is your default. To do this, run the following command:
sudo update-alternatives --config java
Choose the sun version as your default by entering the appropriate number.
2. Then make sure your launcher command is correct. It should be:
sudo ipblock -g

Sources: iplist cli reference