The different in making apple
When Steve Jobs (co-founder of Apple Inc.) resigned from Apple he created NeXT Computer Inc. Which used NeXTSTEP operating system based on Objective-C. Those computers were not very famous but were used in academics and research. Afterwards Apple bought this company and MAC OS X is evolved from that operating system (NeXTSTEP) so they continued to use it. Now all the apple development (Mac, iPhone, iPad and iPod) is done in Objective-C. That’s why they don't use JAVA. Also objective-C is a powerful language like Java or any other.
Comparing with Java, Objective – C is an object oriented language just like Java but Java does not have Pointers and Objective-C does.