I've been programming for about 2 years, and so far Java is all I know.
When I made the switch from BlueJ to eclipse I noticed my old projects ran much faster. What would be the reason for this, as far as I knew the executing of java byte code is handled by the JVM and I still had the same JVM after I switched. Other than that does eclipse have had a different compiler? That's the only other thing I could think of.
I timed it, the average runtime for, we'll call it A(100), in blueJ was 1 Minutes; 8 Seconds; 846 Milliseconds. In eclipse A(100) only took 8 Seconds; 459 Milliseconds. I've also noticed the increase for all my other programs too. I haven't measured those yet but the difference is definitely noticeable.
A() is a function that does alot of computation than prints of a chart of information based on what it found, fyi.