This class is used as a demonstration of speed of execution differences between various looping alternatives, from the original (pre JDK 5) for-loop to modern stream/lambda techniques.
While these tests are open to vagaries caused by things like warm-up time, fit-for-purpose, amount and difficulty of work done, etc., they are still useful in contemplating which technique you may want to use.
It should come as no surprise that the original for-loop is almost always the fastest, with the one exception being the Lambda Stream loop in the Double test.
For best results run the tests multiple times. You will get different results each time, though the overall ranking will be the same. You should also change the size of the collection (mostly smaller) to again see different results, though not as great as you might expect.