Fixed Index (override hashcode)

Signed-off-by: Nico Rutishauser <nr@hotmail.ch>
Sonar issues on the client

Signed-off-by: Nico Rutishauser <nr@hotmail.ch>
Stick to parent's hash code implementation

although findbugs forces me to override the method explicitely

Signed-off-by: Nico Rutishauser <nr@hotmail.ch>