Bug With Java

Hi !
I'm sorry if my English isn't truly good 'cause.
So, i'll explain my "bug" :
When i launch minecraft by clicking on "Play" a error appear, it's says this :
-"Error: opening registry key 'Software\JavaSoft\Java Runtime Environment'"
-"Error: could not find java.dll"
-"Error: Could not find Java SE Runtime Environment"
Thanks you in advance for your help