How To Check If JDK Is 32-bit or 64-bit?

If a JDK is 64-bit, executing

java -version

will usually include a

64-bit Server VM

in the result. And just to be sure, try

java -d64 version

If it is NOT a 64-bit, you will get an error message saying something like

Error: This Java instance does not support a 64-bit JVM. Please install the desired version.