No. JMeter is a load-test tool. It can stress-test your application by generating a lot of load, and measure response times and throughput. But you still need to profile your code. Java has a built-in profiling tool -hprof- (which very much impacts performance, so you can't use it and still expect meaningful performance numbers), and an API for external tools (JVMPI). If you search through SourceForge you'll find plenty of options; I can't comment on their quality. One commercial tool I've heard good things about is JProbe.
Ping & DNS - updated with new look and Ping home screen widget