Adding jars to your classpath in Xcode
It's difficult to reference external .jar files in the classpath passed to the Java compiler by Xcode. Or, at least, it took me a long time to figure out how it works. The secret is adding the .jar file to the "Java Classes" search path of the project's target. The tricky part is that the dialog box that appears when you press the "+" sign will only let you select a directory - pick the directory containing the .jar, press "Add", and then double-click the newly added entry. Simply append the name of the .jar file to the directory path. Then it will be added to the classpath passed to the Java compiler. (In the expert view, the JAVA_CLASS_SEARCH_PATHS variable will display a space-separated list of the .jars.)
Note that this won't add the .jar to the runtime classpath. You'll also need to add it to the Classpath list in the "Pure Java Specific" section of the Target properties.