why java version not updated on mac machine?

I checked my java version from terminal .I got this information

Last login: Sun Mar 15 08:46:08 on ttys000
localhost:~ naveenkumar$ java -version
java version "1.7.0_10"
Java(TM) SE Runtime Environment (build 1.7.0_10-b18)
Java HotSpot(TM) 64-Bit Server VM (build 23.6-b04, mixed mode)
localhost:~ naveenkumar$ 

I install new java 1.8 JRE .close my terminal .Agan i type java -version .I found the same version .

why ? how to upgrade java version.