Java version required to use OKTA SAML Tool Kit-3.1.2

We are trying to integrate OKTA in our application via SAML2.0.
So downloaded OKTA SAML tool kit(3.1.2) from my developer account and when i try to run a simple application by adding this jar from JDeveloper(IDE) which uses Java1.7.0_79,getting the below error.
java.lang.UnsupportedClassVersionError: com/okta/saml/SAMLValidator : Unsupported major.minor version 52.0.
I did google for this error and found the current available tool kit requires java 1.8 or above.
Is this true …?
If yes where can i get the tool kit for older java versions(1.7) as our application infrastructure currently does not support java1.8 or any other(not provided OKTA) open saml tool kit available for integration with OKTA.
Please let me know.
Thanks in advance.

Can anyone please answer my question.
If there is no OKTA SAML tool kit available for the earlier java versions (i.e <1.8,we are using java1.7),please let me know which other tool kit can i use…?
Thanks in advance…