accidental installation

I've accidentally installed something after entering my password, while java update. Should i re-install operation system, disc erase...etc ???

If it was a Java update you can see that in your >System Preferences>Java

If you are unsure,

To see entire history of what you downloaded, from terminal copy and paste:

sqlite3 ~/Library/Preferences/com.apple.LaunchServices.QuarantineEventsV* 'select LSQuarantineDataURLString from LSQuarantineEvent'

or from your Finder>Go>Go To Folder> copy and paste:

/Applications/Utilities/System Information.app

look at Software>Installations (you can sort by install date.)

Run Etrecheck and post the report. It's an excellent diagnostic and snapshot of your Mac's system and HD for evaluation. If there's an unusual app that's been installed you will be able to see it and find out where it's located. There is no personal info included in the report.

Use the Add Text button to add the report to your reply:

Post a report from this please...

EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac.

http://www.etresoft.com/etrecheck

There is also Malwarebytes…

https://www.malwarebytes.com/mac/

What did you accidentally install? What OS? What model/year computer?