JDK 32 or 64 bit

To find out if JDK is 32 or 64 bit, run java -version.

/opt/jdk/bin/java -version

A 64 bit JDK would  output
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)

A 32 bit JDK would  output
java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b06)
Java HotSpot(TM) Server VM (build 17.0-b16, mixed mode)

If you don't see 64 bit in your output, most probably the JDK is 32-bit