OpenJDK 25 : Install2025/09/30

	Install OpenJDK.
[1]	Install OpenJDK 25 and run a test program.

root@dlp:~#

apt -y install openjdk-25-jdk

root@dlp:~#

cat > /etc/profile.d/java.sh <<'EOF'
export JAVA_HOME=$(dirname $(dirname $(readlink $(readlink $(which java)))))
export PATH=$PATH:$JAVA_HOME/bin
EOF

root@dlp:~#

source /etc/profile.d/java.sh

root@dlp:~#

java --version

openjdk 25-ea 2025-09-16
OpenJDK Runtime Environment (build 25-ea+32-Debian-1)
OpenJDK 64-Bit Server VM (build 25-ea+32-Debian-1, mixed mode, sharing)

# verify to create test program

root@dlp:~# cat > java_test.java <<'EOF'
class java_test {
    public static void main(String[] args) {
        System.out.println("Hello Java World !");
    }
}
EOF

root@dlp:~#

javac java_test.java

root@dlp:~#

java java_test

Hello Java World !

[2]	If you installed multiple version of Java from official repository, it's possible to switch them with [update-alternatives].

root@dlp:~#

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-25-openjdk-amd64/bin/java   2511      auto mode
  1            /usr/lib/jvm/java-21-openjdk-amd64/bin/java   2111      manual mode
  2            /usr/lib/jvm/java-25-openjdk-amd64/bin/java   2511      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-21-openjdk-amd64/bin/java to provide /usr/bin/java (java) in manual mode

root@dlp:~#

update-alternatives --config javac

There are 2 choices for the alternative javac (providing /usr/bin/javac).

  Selection    Path                                          Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-25-openjdk-amd64/bin/javac   2511      auto mode
  1            /usr/lib/jvm/java-21-openjdk-amd64/bin/javac   2111      manual mode
  2            /usr/lib/jvm/java-25-openjdk-amd64/bin/javac   2511      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-21-openjdk-amd64/bin/javac to provide /usr/bin/javac (javac) in manual mode

root@dlp:~#

java -version

openjdk version "25-ea" 2025-09-16
OpenJDK Runtime Environment (build 25-ea+32-Debian-1)
OpenJDK 64-Bit Server VM (build 25-ea+32-Debian-1, mixed mode, sharing)

root@dlp:~#

javac -version

javac 25-ea

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