aaron@Server:~$ sudo apt install openjdk-9-jdk
[sudo] password for aaron: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  account-plugin-facebook account-plugin-flickr account-plugin-google ant
  ant-optional antlr3 aspectj default-jdk default-jdk-headless
  fonts-opensymbol fonts-stix gir1.2-accounts-1.0 gir1.2-gdata-0.0
  gir1.2-goa-1.0 gir1.2-json-1.0 gir1.2-rb-3.0 gir1.2-secret-1
  gir1.2-signon-1.0 gir1.2-totem-1.0 gir1.2-totem-plparser-1.0
  gnome-video-effects grilo-plugins-0.2-base guile-2.0-libs javahelp2 junit4
  libabw-0.1-1v5 libandroid-properties1 libantlr-java libantlr3-runtime-java
  libasm4-java libaspectj-java libboost-date-time1.58.0 libbsh-java
  libcdr-0.1-1 libclucene-contribs1v5 libclucene-core1v5 libcmis-0.5-5v5
  libcolamd2.9.1 libdmapsharing-3.0-2 libe-book-0.1-1 libeot0
  libequinox-osgi-java libetonyek-0.1-1 libevent-2.0-5 libexttextcat-2.0-0
  libexttextcat-data libfelix-framework-java libfelix-main-java
  libfreehand-0.1-1 libgc1c2 libgeronimo-jpa-2.0-spec-java
  libgeronimo-osgi-support-java libgexiv2-2 libgmime-2.6-0 libgom-1.0-0
  libgom-1.0-common libgpod-common libgpod4 libgrilo-0.2-1 libhamcrest-java
  libjasper1 libjcommander-java libjna-java libjna-jni libjna-platform-java
  liblangtag-common liblangtag1 liblircclient0 liblua5.2-0 libmessaging-menu0
  libmhash2 libmspub-0.1-1 libmwaw-0.3-3 libmythes-1.2-0 libnatpmp1
  libnb-org-openide-modules-java libnb-org-openide-util-java
  libnb-org-openide-util-lookup-java libnb-platform18-java libneon27-gnutls
  libodfgen-0.1-1 liborcus-0.10-0v5 libosgi-annotation-java
  libosgi-compendium-java libosgi-core-java libosgi-foundation-ee-java
  liboxideqt-qmlplugin liboxideqtcore0 liboxideqtquick0 libpagemaker-0.0-0
  libqqwing2v5 libqt5positioning5 libquvi-scripts libquvi7 libraptor2-0
  librasqal3 libraw15 librdf0 librevenge-0.0-0 librhythmbox-core9
  libservlet3.0-java libservlet3.1-java libsgutils2-2 libstringtemplate-java
  libstringtemplate4-java libsuitesparseconfig4.4.6 libswing-layout-java
  libtotem-plparser-common libtotem-plparser18 libtotem0 libvisio-0.1-1
  libvisualvm-jni libwpd-0.10-10 libwpg-0.3-3 libwps-0.4-4 libyajl2
  libyaml-snake-java lp-solve media-player-info openjdk-8-jdk
  openjdk-8-jdk-headless oxideqt-codecs python3-blinker python3-cffi-backend
  python3-cryptography python3-httplib2 python3-idna python3-jwt python3-mako
  python3-oauthlib qml-module-qt-labs-folderlistmodel
  qml-module-qt-labs-settings qml-module-ubuntu-onlineaccounts
  qml-module-ubuntu-web qtdeclarative5-accounts-plugin
  qtdeclarative5-qtquick2-plugin rhythmbox-data testng totem-common
  transmission-common unity-webapps-qml uno-libs3 ure
Use 'sudo apt autoremove' to remove them.
Suggested packages:
  openjdk-9-demo openjdk-9-source visualvm
The following NEW packages will be installed:
  openjdk-9-jdk
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/16.6 kB of archives.
After this operation, 58.4 kB of additional disk space will be used.
(Reading database ... 211928 files and directories currently installed.)
Preparing to unpack .../openjdk-9-jdk_9~b114-0ubuntu1_amd64.deb ...
Unpacking openjdk-9-jdk:amd64 (9~b114-0ubuntu1) ...
dpkg: error processing archive /var/cache/apt/archives/openjdk-9-jdk_9~b114-0ubuntu1_amd64.deb (--unpack):
 trying to overwrite '/usr/lib/jvm/java-9-openjdk-amd64/include/linux/jawt_md.h', which is also in package openjdk-9-jdk-headless:amd64 9~b114-0ubuntu1
Errors were encountered while processing:
 /var/cache/apt/archives/openjdk-9-jdk_9~b114-0ubuntu1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
aaron@Server:~$