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Come installare Java su Ubuntu 22.04


Installare Java su Ubuntu 22.04

Obiettivo

Java è uno dei linguaggi di programmazione più famosi al mondo. Negli ultimi anni si è diffuso al punto da diventare un linguaggio imprescindibile nel mondo dello sviluppo. Per ulteriori informazioni su tutte le funzionalità del linguaggio Java, consulta la documentazione ufficiale.


In questo tutorial imparerai a installare il Java Development Kit (JDK) su una distribuzione Linux Ubuntu 22.04.

 

Requisiti

Questo tutorial presuppone che tu possieda un VPS, un server Bare Metal o, come nel nostro esempio, un’istanza Compute OVHcloud su Ubuntu 22.04. Dovresti anche possedere conoscenze di base sull’uso della riga di comando. Se hai bisogno di aiuto per installare un’istanza Public Cloud con Ubuntu 22.04, consulta la guida Creare e connettersi a un’istanza Public Cloud.

 

Procedura

In questo tutorial viene utilizzato OpenJDK nella versione open source. Sono inoltre disponibili numerose versioni con licenza presso diversi fornitori (Oracle, Microsoft, AWS...).

In questo tutorial installerai OpenJDK, lo utilizzerai e imparerai a passare da una versione all’altra.

Nel momento in cui viene pubblicato questo tutorial, l'ultima versione LTS di Java è 17.x e l'ultima versione GA è 18.x.

 

Installare la versione OpenJDK LTS

Per installare Java su Ubuntu, utilizza il comando apt-get:

sudo apt-get update && apt-get -y install openjdk-17-jdk

Output:

$ sudo apt-get update && apt-get -y install openjdk-17-jdk
Hit:1 http://security.ubuntu.com/ubuntu jammy-security InRelease
Hit:2 http://nova.clouds.archive.ubuntu.com/ubuntu jammy InRelease
Hit:3 http://nova.clouds.archive.ubuntu.com/ubuntu jammy-updates InRelease
Hit:4 http://nova.clouds.archive.ubuntu.com/ubuntu jammy-backports InRelease
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  adwaita-icon-theme alsa-topology-conf alsa-ucm-conf at-spi2-core ca-certificates-java dconf-gsettings-backend dconf-service fontconfig fontconfig-config
  fonts-dejavu-core fonts-dejavu-extra gsettings-desktop-schemas gtk-update-icon-cache hicolor-icon-theme humanity-icon-theme java-common libasound2 libasound2-data
  libatk-bridge2.0-0 libatk-wrapper-java libatk-wrapper-java-jni libatk1.0-0 libatk1.0-data libatspi2.0-0 libavahi-client3 libavahi-common-data libavahi-common3
  libcairo-gobject2 libcairo2 libcups2 libdatrie1 libdconf1 libdeflate0 libdrm-amdgpu1 libdrm-intel1 libdrm-nouveau2 libdrm-radeon1 libfontconfig1 libfontenc1
  libgail-common libgail18 libgdk-pixbuf-2.0-0 libgdk-pixbuf2.0-bin libgdk-pixbuf2.0-common libgif7 libgl1 libgl1-amber-dri libgl1-mesa-dri libglapi-mesa libglvnd0
  libglx-mesa0 libglx0 libgraphite2-3 libgtk2.0-0 libgtk2.0-bin libgtk2.0-common libharfbuzz0b libice-dev libice6 libjbig0 libjpeg-turbo8 libjpeg8 liblcms2-2 libllvm13
  libpango-1.0-0 libpangocairo-1.0-0 libpangoft2-1.0-0 libpciaccess0 libpcsclite1 libpixman-1-0 libpthread-stubs0-dev librsvg2-2 librsvg2-common libsm-dev libsm6
  libthai-data libthai0 libtiff5 libvulkan1 libwayland-client0 libwebp7 libx11-dev libx11-xcb1 libxau-dev libxaw7 libxcb-dri2-0 libxcb-dri3-0 libxcb-glx0
  libxcb-present0 libxcb-randr0 libxcb-render0 libxcb-shape0 libxcb-shm0 libxcb-sync1 libxcb-xfixes0 libxcb1-dev libxcomposite1 libxcursor1 libxdamage1 libxdmcp-dev
  libxfixes3 libxft2 libxi6 libxinerama1 libxkbfile1 libxmu6 libxpm4 libxrandr2 libxrender1 libxshmfence1 libxt-dev libxt6 libxtst6 libxv1 libxxf86dga1 libxxf86vm1
  mesa-vulkan-drivers openjdk-17-jdk-headless openjdk-17-jre openjdk-17-jre-headless session-migration ubuntu-mono x11-common x11-utils x11proto-dev xorg-sgml-doctools
  xtrans-dev
...
update-alternatives: using /usr/lib/jvm/java-17-openjdk-amd64/bin/jhsdb to provide /usr/bin/jhsdb (jhsdb) in auto mode
Setting up libgtk2.0-0:amd64 (2.24.33-2ubuntu2) ...
Setting up humanity-icon-theme (0.6.16) ...
Setting up libgail18:amd64 (2.24.33-2ubuntu2) ...
Setting up libgtk2.0-bin (2.24.33-2ubuntu2) ...
Setting up libgail-common:amd64 (2.24.33-2ubuntu2) ...
Setting up openjdk-17-jre:amd64 (17.0.3+7-0ubuntu0.22.04.1) ...
Setting up ubuntu-mono (20.10-0ubuntu2) ...
Setting up openjdk-17-jdk:amd64 (17.0.3+7-0ubuntu0.22.04.1) ...
update-alternatives: using /usr/lib/jvm/java-17-openjdk-amd64/bin/jconsole to provide /usr/bin/jconsole (jconsole) in auto mode
Processing triggers for ca-certificates (20211016) ...
Updating certificates in /etc/ssl/certs...
0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...

done.
done.
Processing triggers for libglib2.0-0:amd64 (2.72.1-1) ...
Processing triggers for libc-bin (2.35-0ubuntu3) ...
Processing triggers for man-db (2.10.2-1) ...
Setting up at-spi2-core (2.44.0-3) ...
Processing triggers for libgdk-pixbuf-2.0-0:amd64 (2.42.8+dfsg-1) ...
Scanning processes...                                                                                                                                                     
Scanning candidates...                                                                                                                                                    
Scanning linux images...                                                                                                                                                  

Restarting services...
 /etc/needrestart/restart.d/systemd-manager
 systemctl restart packagekit.service postgresql@14-main.service ssh.service systemd-journald.service systemd-networkd.service systemd-resolved.service systemd-timesyncd.service systemd-udevd.service udisks2.service
Service restarts being deferred:
 systemctl restart systemd-logind.service
 systemctl restart user@1000.service

No containers need to be restarted.

No user sessions are running outdated binaries.

No VM guests are running outdated hypervisor (qemu) binaries on this host.

Verifica l'installazione di Java:

java -version

Output:

$ java - version
openjdk version "17.0.3" 2022-04-19
OpenJDK Runtime Environment (build 17.0.3+7-Ubuntu-0ubuntu0.22.04.1)
OpenJDK 64-Bit Server VM (build 17.0.3+7-Ubuntu-0ubuntu0.22.04.1, mixed mode, sharing)

È consigliabile impostare una variabile d'ambiente JAVA_HOME con il percorso all’installazione JDK.

export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64/ echo $JAVA_HOME

Output:

$ export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64/
$ echo $JAVA_HOME
/usr/lib/jvm/java-17-openjdk-amd64/
$ 

 

Gestire due o più installazioni JDK

Ipotizziamo che tu debba utilizzare un'altra versione JDK per un progetto specifico. Installa la versione specifica di OpenJDK, come mostrato in precedenza.

sudo apt-get -y install openjdk-18-jdk

Output:

$ sudo apt-get -y install openjdk-18-jdk
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  openjdk-18-jdk-headless openjdk-18-jre openjdk-18-jre-headless
Suggested packages:
  openjdk-18-demo openjdk-18-source visualvm libnss-mdns fonts-ipafont-gothic fonts-ipafont-mincho fonts-wqy-microhei | fonts-wqy-zenhei fonts-indic
The following NEW packages will be installed:
  openjdk-18-jdk openjdk-18-jdk-headless openjdk-18-jre openjdk-18-jre-headless
0 upgraded, 4 newly installed, 0 to remove and 12 not upgraded.
Need to get 268 MB of archives.
After this operation, 421 MB of additional disk space will be used.
Get:1 http://nova.clouds.archive.ubuntu.com/ubuntu jammy/universe amd64 openjdk-18-jre-headless amd64 18~36ea-1 [48.0 MB]
Get:2 http://nova.clouds.archive.ubuntu.com/ubuntu jammy/universe amd64 openjdk-18-jre amd64 18~36ea-1 [180 kB]
Get:3 http://nova.clouds.archive.ubuntu.com/ubuntu jammy/universe amd64 openjdk-18-jdk-headless amd64 18~36ea-1 [220 MB]
Get:4 http://nova.clouds.archive.ubuntu.com/ubuntu jammy/universe amd64 openjdk-18-jdk amd64 18~36ea-1 [10.9 kB]
Fetched 268 MB in 5s (58.3 MB/s)           
..
update-alternatives: using /usr/lib/jvm/java-18-openjdk-amd64/bin/jhsdb to provide /usr/bin/jhsdb (jhsdb) in auto mode
Setting up openjdk-18-jdk:amd64 (18~36ea-1) ...
update-alternatives: using /usr/lib/jvm/java-18-openjdk-amd64/bin/jconsole to provide /usr/bin/jconsole (jconsole) in auto mode
Processing triggers for hicolor-icon-theme (0.17-2) ...
Scanning processes...                                                                                                                                                     
Scanning candidates...                                                                                                                                                    
Scanning linux images...                                                                                                                                                  

Restarting services...
Service restarts being deferred:
 systemctl restart systemd-logind.service
 systemctl restart user@1000.service

No containers need to be restarted.

No user sessions are running outdated binaries.

No VM guests are running outdated hypervisor (qemu) binaries on this host.

Verifica la nuova installazione:

java -version

Output:

$ java - version
openjdk version "18-ea" 2022-03-22
OpenJDK Runtime Environment (build 18-ea+36-Ubuntu-1)
OpenJDK 64-Bit Server VM (build 18-ea+36-Ubuntu-1, mixed mode, sharing)

Quindi imposta la variabile d’ambiente JAVA_HOME:

export JAVA_HOME=/usr/lib/jvm/java-18-openjdk-amd64/ echo $JAVA_HOME

Output:

$ export JAVA_HOME=/usr/lib/jvm/java-18-openjdk-amd64/
$ echo $JAVA_HOME
/usr/lib/jvm/java-18-openjdk-amd64/
$ 

Non è molto pratico tornare alla versione 17. Fortunatamente, si può utilizzare lo strumento update-alternatives.

sudo update-alternatives --config java

Output:

$ sudo update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                         Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-18-openjdk-amd64/bin/java   1811      auto mode
  1            /usr/lib/jvm/java-17-openjdk-amd64/bin/java   1711      manual mode
  2            /usr/lib/jvm/java-18-openjdk-amd64/bin/java   1811      manual mode

Press  to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/lib/jvm/java-17-openjdk-amd64/bin/java to provide /usr/bin/java (java) in manual mode

Verifica che sia stata selezionata la nuova versione java.

java -version

Output:

$ java - version
openjdk version "17.0.3" 2022-04-19
OpenJDK Runtime Environment (build 17.0.3+7-Ubuntu-0ubuntu0.22.04.1)
OpenJDK 64-Bit Server VM (build 17.0.3+7-Ubuntu-0ubuntu0.22.04.1, mixed mode, sharing)

⚠️ Attenzione!⚠️ Se è stata impostata la variabile d’ambiente JAVA_HOME, è necessario aggiornarla con il percorso corretto.

 

Testare l'installazione JDK

Testa l'installazione di Java creando un'applicazione Hello World. Crea un file HelloWorld.java e incolla nel file il seguente codice:

public class HelloWorld { public static void main(String[] args) { System.out.println("👋 Hello World!"); } }

Salva e compila il file, quindi eseguilo.

javac HelloWorld.java java HelloWorld

Output:

$ javac HelloWorld.java 
$ java HelloWorld.java 
👋 Hello World!

Ci siamo: hai installato e configurato correttamente OpenJDK su Ubuntu 22.04.