The list of improvements is quite long, actually:
- Server Cipher Suite Preference
- Strong Server Ephemeral Diffie-Hellman Parameters
- Authenticated (GCM) Suites
- Hardware Acceleration on Intel and AMD processors
- Server-Side SNI Support
- Ability to disable client-initiated renegotiation
- TLS 1.2 enabled by default in client mode
- Clients support Ephemeral DH over 1024 bits
More details here: http://blog.ivanristic.com/2014/03/ssl-tls-improvements-in-j...
And there are more security improvements documented here: http://openjdk.java.net/projects/jdk8/features#core/sec