There can be two reasons for this warning:
1. You have installed the wrong Java JDK8 package.
Please ensure that you have downloaded the 64-bit JDK8 and remove your current 32-bit JDK8.
2. It's a warning due to the Hadoop libraries being compiled for 32bits. You are probably running on a 64bit OS.
It's safe to ignore this warning.
For more information regarding the same, refer the following video: