OpenJDK 17 : インストール2021/09/23

	OpenJDK をインストールします。
[1]	OpenJDK 17 をインストールします。JRE のみで良い場合は [openjdk-17-jre] を指定します。

root@dlp:~#

apt -y install openjdk-17-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 17-ea 2021-09-14
OpenJDK Runtime Environment (build 17-ea+19-Debian-1)
OpenJDK 64-Bit Server VM (build 17-ea+19-Debian-1, mixed mode, sharing)

# テストプログラムを作成して動作確認

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]	複数バージョンをインストールしている場合は [alternatives] で切り替え可能です。

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-17-openjdk-amd64/bin/java   1711      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java   1111      manual mode
  2            /usr/lib/jvm/java-17-openjdk-amd64/bin/java   1711      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2

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-17-openjdk-amd64/bin/javac   1711      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/javac   1111      manual mode
  2            /usr/lib/jvm/java-17-openjdk-amd64/bin/javac   1711      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2

root@dlp:~#

java --version

openjdk 17-ea 2021-09-14
OpenJDK Runtime Environment (build 17-ea+19-Debian-1)
OpenJDK 64-Bit Server VM (build 17-ea+19-Debian-1, mixed mode, sharing)