keytool error: java.io.IOException: Invalid keystore format

While listing the certificates from .oamkeystore was getting below error:

oracle@aj-oamr2 fmwconfig]$ ls -la .oamkeystore

-rw-r-----. 1 oracle oinstall 10441 Feb  2 11:33 .oamkeystore

[oracle@aj-oamr2 fmwconfig]$ keytool -list -keystore .oamkeystore -storepass <password>
keytool error: java.io.IOException: Invalid keystore format

The problem is with the keystore type which needs to be also defined in the above command.

Example:

[oracle@aj-oamr2 fmwconfig]$ keytool -list -keystore .oamkeystore -storetype JCEKS -storepass <password>

Keystore type: JCEKS
Keystore provider: SunJCE

Your keystore contains 12 entries

adminserver, Feb 2, 2016, PrivateKeyEntry,
Certificate fingerprint (SHA1): C2:48:94:91:54:A0:BC:5A:11:A7:42:EC:27:9C:8B:57:4C:D0:07:0E
coherence, Feb 2, 2016, SecretKeyEntry,