$ sudo apt-get purge --no-install-recommends --ignore-missing --no-download openjdk-6-jre
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  openjdk-7-jre openjdk-7-jre-headless openjdk-7-jre-lib
Suggested packages:
  icedtea-7-plugin libnss-mdns sun-java6-fonts fonts-ipafont-gothic fonts-ipafont-mincho ttf-wqy-microhei ttf-wqy-zenhei ttf-indic-fonts-core ttf-telugu-fonts
  ttf-oriya-fonts ttf-kannada-fonts ttf-bengali-fonts
Recommended packages:
  icedtea-7-jre-jamvm
The following packages will be REMOVED:
  default-jre* icedtea-netx* openjdk-6-jre*
The following NEW packages will be installed:
  openjdk-7-jre openjdk-7-jre-headless openjdk-7-jre-lib
0 upgraded, 3 newly installed, 3 to remove and 2 not upgraded.
Need to get 41.1 MB of archives.
After this operation, 55.3 MB of additional disk space will be used.
Do you want to continue [Y/n]?
Unable to correct missing packages.
E: Aborting install.