what will happen if i disable TLS1.2 on my LTM version 10.2.3? would it be good if i disable it in ciphers

No. Why would you want to do this?

i am facing an issue, when I disable TLS1.2 on java console it works fine but when it is enable TLS1.2 on java version 1.8_0_25. so wanted to check by disbaling TLS1.2 on F5 LTM.

OK, well you can do this quite easily by modifying the cipher string used in the SSLClient profile assigned to the Virtual Server (VS). A string like this should work: !SSLv2:ALL:!DH:!ADH:!EDH:@SPEED. Obviously I'd only recommend this temporarily, whilst troubleshooting your issue.

Ideally the VS would be using a custom profile so this change wouldn't affect other VSs and related traffic.

I got to know from F5 that we can not disable TLS1.2 in 10.2.3 version.