OpenJDK 21 : インストール2025/02/12

	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。

[root@dlp ~]#

dnf -y install java-21-openjdk java-21-openjdk-devel

[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 version "21.0.5" 2024-10-15 LTS
OpenJDK Runtime Environment (Red_Hat-21.0.5.0.11-1) (build 21.0.5+11-LTS)
OpenJDK 64-Bit Server VM (Red_Hat-21.0.5.0.11-1) (build 21.0.5+11-LTS, 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]	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 [alternatives] で切り替え可能です。

[root@dlp ~]#

alternatives --config java


There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
   1           /usr/lib/jvm/java-25-openjdk/bin/java
*+ 2           /usr/lib/jvm/java-21-openjdk/bin/java

Enter to keep the current selection[+], or type selection number: 2

[root@dlp ~]#

alternatives --config javac


There are 2 programs which provide 'javac'.

  Selection    Command
-----------------------------------------------
   1           /usr/lib/jvm/java-25-openjdk/bin/javac
*+ 2           /usr/lib/jvm/java-21-openjdk/bin/javac

Enter to keep the current selection[+], or type selection number: 2

[root@dlp ~]#

java --version

openjdk version "21.0.5" 2024-10-15 LTS
OpenJDK Runtime Environment (Red_Hat-21.0.5.0.11-1) (build 21.0.5+11-LTS)
OpenJDK 64-Bit Server VM (Red_Hat-21.0.5.0.11-1) (build 21.0.5+11-LTS, mixed mode, sharing)

[root@dlp ~]#

javac --version

javac 21.0.5