What do you exactly mean by that question? Speed in Java apps can be determined by many factors. One of them is exection time. The lesss execution time you have, faster is your program. Other factor is memory utilization, sometimes if you can afford to utilize more memory(that too wisely), again your program will be fast. Sometimes its a trade off between the two.
Basically, there is no single authoritative definition.
Why do you ask?
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus