For java, I would recommend Netbeans. Its a great IDE. Pre-installs ant and tomcat,SAX and DOM APIs. Also has plugins for J2ME. So its a complete package for anything related to Java.
Maybe. It depends on what you're doing with Borland C++. If you're using it to develop Windows software (and using Borland libraries), you probably don't want to try that with Xcode.
If, on the other hand, you're just looking for C++ and Java development tools then OS X has plenty. Like someone else posted, developer.apple.com is a good place to start.