1) lslpp -l |grep -i java

or

1) which java
2) $(which java) -version

Example:

testlab:/# lslpp -l |grep -i java
Java5.sdk 5.0.0.620 COMMITTED Java SDK 32-bit
Java5_64.sdk 5.0.0.620 COMMITTED Java SDK 64-bit
Java6.sdk 6.0.0.561 COMMITTED Java SDK 32-bit
Java71_64.jre 7.1.0.0 COMMITTED Java SDK 64-bit Java Runtime
Java71_64.sdk 7.1.0.0 COMMITTED Java SDK 64-bit Development
idebug.rte.olt.Java
ifor_ls.java.gui 6.1.0.0 COMMITTED License Use Management Runtime
Java GUI
ifor_ls.msg.en_US.java.gui
6.1.0.0 COMMITTED LUM Java GUI Messages – U.S.
2.5.4.0 COMMITTED RSCT GUI JAVA Msgs – U.S.
2.5.4.0 COMMITTED RSCT RMC JAVA Msgs – U.S.
Java5.sdk 5.0.0.620 COMMITTED Java SDK 32-bit
Java5_64.sdk 5.0.0.620 COMMITTED Java SDK 64-bit
Java6.sdk 6.0.0.561 COMMITTED Java SDK 32-bit
Java71_64.jre 7.1.0.0 COMMITTED Java SDK 64-bit Java Runtime
testlab:/#

testlab:/# which java
/usr/java6/jre/bin/java
testlab:/#

testlab:/# $(which java) -version
java version “1.6.0”
Java(TM) SE Runtime Environment (build pap3260sr16fp26-20160508_01(SR16 FP26))
IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 AIX ppc-32 jvmap3260sr16fp25-20160413_299433 (JIT enabled, AOT enabled)
J9VM – 20160413_299433
JIT – r9_20160328_114196
GC – GA24_Java6_SR16_20160413_1159_B299433)
JCL – 20160507_01
testlab:/#