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XCode is really a great IDE for Java. It supports it, but isn't built for it.

Install Eclipse or NetBeans, they are built for Java and in Java.

To answer your question, no the Collections interface isn't built into Java, it is another series of classes that you have to import.

Download the Java doc from Sun.

Collections, e.g. ArrayList, Vector, Map, etc are all in the package java.util
 
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