emerge -C java-config
emerge gcj-jdk

...

!!! ERROR: The active vm could not be found
!!! ERROR: The active vm could not be found
!!! ERROR: The active vm could not be found
!!! ERROR: The active vm could not be found
!!! ERROR: The active vm could not be found
!!! ERROR: The active vm could not be found
!!! ERROR: The active vm could not be found

>>> Install eclipse-ecj-3.2-r1 into /var/tmp/portage/eclipse-ecj-3.2-r1/image/ category dev-java

!!! ERROR: dev-java/eclipse-ecj-3.2-r1 failed.
Call stack:
  ebuild.sh, line 1546:   Called dyn_install
  ebuild.sh, line 1020:   Called src_install
  eclipse-ecj-3.2-r1.ebuild, line 63:   Called java-pkg_dojar 'ecj.jar'
  java-utils-2.eclass, line 277:   Called die

!!! ecj.jar does not exist
!!! If you need support, post the topmost build error, and the call stack if relevant.

!!! When you file a bug report, please include the following information:
GENTOO_VM=  CLASSPATH="" JAVA_HOME=""
JAVACFLAGS="-target 1.4" COMPILER=""
and of course, the output of emerge --info
!!! This ebuild is from an overlay: '/usr/local/portage'