OpenJDK 21 : インストール2025/12/05

	OpenJDK 21 をインストールします。
[1]	JRE のみで良い場合は [java-21-openjdk] のみの指定で OK、コンパイラーもインストールする場合は [java-21-openjdk-devel] もあわせてインストールします。

dlp:~ #

zypper -n install java-21-openjdk java-21-openjdk-devel

dlp:~ #

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

dlp:~ #

source /etc/profile.d/java.sh

dlp:~ #

java -version

openjdk version "21.0.9" 2025-10-21
OpenJDK Runtime Environment (build 21.0.9+10-suse-1600-x8664)
OpenJDK 64-Bit Server VM (build 21.0.9+10-suse-1600-x8664, mixed mode, sharing)

# テストプログラムを作成して動作確認

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

dlp:~ #

javac java_test.java

dlp:~ #

java java_test

Hello Java World !

[2]	公式リポジトリから複数バージョンをインストールしている場合は [update-alternatives] で切り替え可能です。

dlp:~ #

update-alternatives --config java

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

  Selection    Path                                    Priority   Status
------------------------------------------------------------
* 0            /usr/lib64/jvm/jre-25-openjdk/bin/java   3505      auto mode
  1            /usr/lib64/jvm/jre-21-openjdk/bin/java   3105      manual mode
  2            /usr/lib64/jvm/jre-25-openjdk/bin/java   3505      manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/lib64/jvm/jre-21-openjdk/bin/java to provide /usr/bin/java (java) in manual mode

dlp:~ #

update-alternatives --config javac

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

  Selection    Path                                      Priority   Status
------------------------------------------------------------
* 0            /usr/lib64/jvm/java-25-openjdk/bin/javac   3505      auto mode
  1            /usr/lib64/jvm/java-21-openjdk/bin/javac   3105      manual mode
  2            /usr/lib64/jvm/java-25-openjdk/bin/javac   3505      manual mode

Press <enter> to keep the current choice[*], or type selection number: 1
update-alternatives: using /usr/lib64/jvm/java-21-openjdk/bin/javac to provide /usr/bin/javac (javac) in manual mode

dlp:~ #

java -version

openjdk version "21.0.9" 2025-10-21
OpenJDK Runtime Environment (build 21.0.9+10-suse-1600-x8664)
OpenJDK 64-Bit Server VM (build 21.0.9+10-suse-1600-x8664, mixed mode, sharing)

dlp:~ #

javac -version

javac 21.0.9