This is not true. The runtime environment for Java is capable of changing the program on the fly in response to dynamically determined bottlenecks. To implement such a system in C would be to re-implement Java.
What you cannot do in C/C++ that you can in Java is respond to program inefficiencies at runtime, with runtime knowledge.
What you cannot do in C/C++ that you can in Java is respond to program inefficiencies at runtime, with runtime knowledge.