eclipse java processor

Java VM – Eclipse using my cores?

I have this question about the JVM running my Java code. My friend has a 2.4 or 2.5GHz dual core while I have a 2GHz quad core. Now my question is: does Java use all the cores or just one? My friend thought Java used 1 core and so he would have the better running time because his core has a higher clock rate than mine.