If i want the JDK for my Mac, where should I look for it?

The JDK is already installed on Mac OS X 10.5. If you go to /Applications/Utilities you will see Java Preferences. There you can select between the versions of Java you would like to use, including version 6 (6 is only 64-bit so if you have a 32-bit Core Duo Macbook you'll have to use SoyLatte).

alt text http://img121.imageshack.us/img121/4249/javapref.jpg

You need to install the Xcode developer tools. The JDK is included there. Before you do that, though, you can check if it is already installed by using javac -version. To find out where it is located, you can run the command which javac, although it will most likely be a symlink to somewhere else.