Mine

cleanTemp() {
	echo "[CLEANING TMP]"
	pushd /var/tmp/portage >/dev/null
	rm -rf *
	popd >/dev/null
}

cleanTemp

echo "[DIGESTING]"
ebuild $1 digest

echo "[BUILDING]"
for a in "4" "5" "6"
do
	JAVA_PKG_STRICT=true JAVA_PKG_FORCE_VM=sun-jdk-1.${a} ebuild $1 install || exit
	cleanTemp
	JAVA_PKG_STRICT=true JAVA_PKG_FORCE_COMPILER="ecj-3.2" JAVA_PKG_FORCE_VM=sun-jdk-1.${a} ebuild $1 install || exit
	cleanTemp
done

JAVA_PKG_STRICT=true JAVA_PKG_FORCE_COMPILER="jikes" ebuild $1 install || exit
cleanTemp
JAVA_PKG_STRICT=true JAVA_PKG_FORCE_COMPILER="jikes" JAVA_PKG_FORCE_VM=sun-jdk-1.4 ebuild $1 install || exit
cleanTemp