Download JRE 5.0 Update 3 from *java.sun.com/j2se/1.5.0/download.jsp
and install.
For Opera 7.54 download Java version(full -15mb approx.) of Opera and Opera 8.0 is by default Java compliant.
Though you should have JRE 5.0 for java to work in Opera. Finally download JRE and you won't need to install Java separately for Opera.