The Java runtime, java, is often in the same bin directory. If the installed version is older (i.e. it is Java 5 and you wish to use the more recent Java 7 release), you should proceed below with downloading and installing a JDK. It is possible that you have the Java runtime (JRE), but not the JDK.
Earlobe piercings typically heal completely within 4 to 6 weeks. However, ear cartilage piercings -- such as a tragus, conch or helix piercing -- do not heal fully for 3 to 6 months. Swelling and redness usually resolve fairly quickly, typically within about a week.
I'd say that for the daith, as with any piercing, you should wait until it is fully healed. Daith piercings, as any other cartilage piercing, can take as little as 3 months to as long as 12 months to fully heal. It ultimately depends on the thickness of the cartilage, how fast your healing is, how well did you maintain it clean, how well did you prevent infections, and other factors.