As long as your FPS is less than the refresh rate, you don't get tearing. If it's not an integer divisor of your framerate, you may get noticeable stutter however. Isn't Java2D supposed to respect your desktop's compositor anyway? That means on windows it should never tear, and on linux it always will.
False. You can get tearing at any FPS, but it's most noticeable at higher frame rates. Picture a road intersection. You just stated that we don't need traffic lights or stop signs as long as the road isn't completely full of cars.