emerge --pretend -1 =java-config-1* =java-config-2*

These are the packages that would be merged, in order:

Calculating dependencies... done!
[blocks B     ] <dev-java/java-config-1.3 (is blocking dev-java/java-config-wrapper-0.12)
[ebuild  N    ] dev-java/java-config-1.2.11-r1  
[ebuild  N    ] app-portage/portage-utils-0.1.20  USE="python" 
[ebuild  N    ] dev-java/java-config-wrapper-0.12  
[ebuild  N    ] dev-java/java-config-2.0.30