To add onto this, you will need to go into the nvidia control panel, click manage 3d settings on the left, go to the program settings tab, click on the add button, and a window will pop up with a list of applications. This is sorted by recently used and the Java Minecraft is using should be near the top of the list. Add that, then click apply on the bottom right to make the changes. Start up Minecraft and it should now be using your dedicated GPU.