Translations:VirtualBox/83/en
From Gentoo Wiki
When the app-emulation/virtualbox package fails to build because the javac command cannot be found (even with a Java JDK (Java Development Kit) and a Java JRE (Java Runtime Environment) installed), it is likely the JRE has been set as the default system-vm. JRE packages do not contain javac. Make sure the correct system-vm (JDK) has been selected using the java-config command and then try rebuilding virtualbox. More information can be found in the Installing a virtual machine section of the Java User Guide.