在Fedora中安装指定版本的JDK
Java开发者不能没有JDK，就像西方不能没有耶路撒冷。
近期准备使用Linux作为开发主力系统，相对比较熟悉的发行版是远古版本的CentOS7，且早已停止维护，就选择了与CentOS同出一源的Fedora。我选择的是 Fedora Workstation 42。系统安装就不过多赘述了，现在版本比较新的Linux发行版的安装都是比较友好的（大部分）。
截至到写这篇文章的时间，最新的Fedora 42默认安装的 OpenJDK版本是 21.0.7，虽然 Java21也是长期支持版（应该是)。但是我目前常用的还是 Java8，所以需要手动安装一个1.8版本的JDK。
介绍两种安装制定版本JDK的方法：
使用dnf安装OpenJDK
首先打开我们的终端模拟器，输入以下命令搜索可以安装的 OpenJDK
dnf search openjdk
可以得到类似下边的输出
仓库更新和加载中:
google-chrome 100% | 2.3 KiB/s | 1.3 KiB | 00m01s
仓库加载完成。
Matched fields: name, summary
ant-openjdk21.noarch: ant binding for openjdk21
java-21-openjdk.x86_64: OpenJDK 21 Runtime Environment
java-21-openjdk-demo.x86_64: OpenJDK 21 Demos
java-21-openjdk-demo-fastdebug.x86_64: OpenJDK 21 Demos optimised with full debugging on
java-21-openjdk-demo-slowdebug.x86_64: OpenJDK 21 Demos unoptimised with full debugging on
java-21-openjdk-devel.x86_64: OpenJDK 21 Development Environment
java-21-openjdk-devel-fastdebug.x86_64: OpenJDK 21 Development Environment optimised with full debugging on
java-21-openjdk-devel-slowdebug.x86_64: OpenJDK 21 Development Environment unoptimised with full debugging on
java-21-openjdk-fastdebug.x86_64: OpenJDK 21 Runtime Environment optimised with full debugging on
java-21-openjdk-headless.x86_64: OpenJDK 21 Headless Runtime Environment
java-21-openjdk-headless-fastdebug.x86_64: OpenJDK 21 Runtime Environment optimised with full debugging on
java-21-openjdk-headless-slowdebug.x86_64: OpenJDK 21 Runtime Environment unoptimised with full debugging on
java-21-openjdk-javadoc.x86_64: OpenJDK 21 API documentation
java-21-openjdk-javadoc-zip.x86_64: OpenJDK 21 API documentation compressed in a single archive
java-21-openjdk-jmods.x86_64: JMods for OpenJDK 21
java-21-openjdk-jmods-fastdebug.x86_64: JMods for OpenJDK 21 optimised with full debugging on
java-21-openjdk-jmods-slowdebug.x86_64: JMods for OpenJDK 21 unoptimised with full debugging on
java-21-openjdk-portable.x86_64: OpenJDK 21 Runtime Environment portable edition
java-21-openjdk-portable-devel.x86_64: OpenJDK 21 Development Environment portable edition
java-21-openjdk-portable-devel-fastdebug.x86_64: OpenJDK 21 Runtime and Development Environment portable edition optimised with full debugging on
java-21-openjdk-portable-devel-slowdebug.x86_64: OpenJDK 21 Runtime and Development Environment portable edition unoptimised with full debugging on
java-21-openjdk-portable-docs.x86_64: OpenJDK 21 API documentation
java-21-openjdk-portable-fastdebug.x86_64: OpenJDK 21 Runtime Environment portable edition optimised with full debugging on
java-21-openjdk-portable-misc.x86_64: OpenJDK 21 miscellany
java-21-openjdk-portable-slowdebug.x86_64: OpenJDK 21 Runtime Environment portable edition unoptimised with full debugging on
java-21-openjdk-portable-sources.x86_64: OpenJDK 21 full patched sources of portable JDK
java-21-openjdk-portable-static-libs.x86_64: OpenJDK 21 libraries for static linking - portable edition
java-21-openjdk-portable-static-libs-fastdebug.x86_64: OpenJDK 21 libraries for static linking - portable edition optimised with full debugging on
java-21-openjdk-portable-static-libs-slowdebug.x86_64: OpenJDK 21 libraries for static linking - portable edition unoptimised with full debugging on
java-21-openjdk-portable-unstripped.x86_64: The OpenJDK 21 runtime environment.
java-21-openjdk-slowdebug.x86_64: OpenJDK 21 Runtime Environment unoptimised with full debugging on
java-21-openjdk-src.x86_64: OpenJDK 21 Source Bundle
java-21-openjdk-src-fastdebug.x86_64: OpenJDK 21 Source Bundle for packages with debugging on and optimisation
java-21-openjdk-src-slowdebug.x86_64: OpenJDK 21 Source Bundle for packages with debugging on and no optimisation
java-21-openjdk-static-libs.x86_64: OpenJDK 21 libraries for static linking
java-21-openjdk-static-libs-fastdebug.x86_64: OpenJDK 21 libraries for static linking optimised with full debugging on
java-21-openjdk-static-libs-slowdebug.x86_64: OpenJDK 21 libraries for static linking unoptimised with full debugging on
java-latest-openjdk.x86_64: OpenJDK 24 Runtime Environment
java-latest-openjdk-demo.x86_64: OpenJDK 24 Demos
java-latest-openjdk-demo-fastdebug.x86_64: OpenJDK 24 Demos optimised with full debugging on
java-latest-openjdk-demo-slowdebug.x86_64: OpenJDK 24 Demos unoptimised with full debugging on
java-latest-openjdk-devel.x86_64: OpenJDK 24 Development Environment
java-latest-openjdk-devel-fastdebug.x86_64: OpenJDK 24 Development Environment optimised with full debugging on
java-latest-openjdk-devel-slowdebug.x86_64: OpenJDK 24 Development Environment unoptimised with full debugging on
java-latest-openjdk-fastdebug.x86_64: OpenJDK 24 Runtime Environment optimised with full debugging on
java-latest-openjdk-headless.x86_64: OpenJDK 24 Headless Runtime Environment
java-latest-openjdk-headless-fastdebug.x86_64: OpenJDK 24 Runtime Environment optimised with full debugging on
java-latest-openjdk-headless-slowdebug.x86_64: OpenJDK 24 Runtime Environment unoptimised with full debugging on
java-latest-openjdk-javadoc.x86_64: OpenJDK 24 API documentation
java-latest-openjdk-javadoc-zip.x86_64: OpenJDK 24 API documentation compressed in a single archive
java-latest-openjdk-jmods.x86_64: JMods for OpenJDK 24
java-latest-openjdk-jmods-fastdebug.x86_64: JMods for OpenJDK 24 optimised with full debugging on
java-latest-openjdk-jmods-slowdebug.x86_64: JMods for OpenJDK 24 unoptimised with full debugging on
java-latest-openjdk-portable.x86_64: OpenJDK 24 Runtime Environment portable edition
java-latest-openjdk-portable-devel.x86_64: OpenJDK 24 Development Environment portable edition
java-latest-openjdk-portable-devel-fastdebug.x86_64: OpenJDK 24 Runtime and Development Environment portable edition optimised with full debugging on
java-latest-openjdk-portable-devel-slowdebug.x86_64: OpenJDK 24 Runtime and Development Environment portable edition unoptimised with full debugging on
java-latest-openjdk-portable-docs.x86_64: OpenJDK 24 API documentation
java-latest-openjdk-portable-fastdebug.x86_64: OpenJDK 24 Runtime Environment portable edition optimised with full debugging on
java-latest-openjdk-portable-misc.x86_64: OpenJDK 24 miscellany
java-latest-openjdk-portable-slowdebug.x86_64: OpenJDK 24 Runtime Environment portable edition unoptimised with full debugging on
java-latest-openjdk-portable-sources.x86_64: OpenJDK 24 full patched sources of portable JDK
java-latest-openjdk-portable-static-libs.x86_64: OpenJDK 24 libraries for static linking - portable edition
java-latest-openjdk-portable-static-libs-fastdebug.x86_64: OpenJDK 24 libraries for static linking - portable edition optimised with full debugging on
java-latest-openjdk-portable-static-libs-slowdebug.x86_64: OpenJDK 24 libraries for static linking - portable edition unoptimised with full debugging on
java-latest-openjdk-portable-unstripped.x86_64: The OpenJDK 24 runtime environment.
java-latest-openjdk-slowdebug.x86_64: OpenJDK 24 Runtime Environment unoptimised with full debugging on
java-latest-openjdk-src.x86_64: OpenJDK 24 Source Bundle
java-latest-openjdk-src-fastdebug.x86_64: OpenJDK 24 Source Bundle for packages with debugging on and optimisation
java-latest-openjdk-src-slowdebug.x86_64: OpenJDK 24 Source Bundle for packages with debugging on and no optimisation
java-latest-openjdk-static-libs.x86_64: OpenJDK 24 libraries for static linking
java-latest-openjdk-static-libs-fastdebug.x86_64: OpenJDK 24 libraries for static linking optimised with full debugging on
java-latest-openjdk-static-libs-slowdebug.x86_64: OpenJDK 24 libraries for static linking unoptimised with full debugging on
maven-openjdk21.noarch: maven binding for openjdk21
openjdk-asmtools-javadoc.noarch: Javadoc for openjdk-asmtools
openjdk-asmtools7-javadoc.noarch: Javadoc for openjdk-asmtools7
xmvn-toolchain-openjdk21.noarch: xmvn-minimal binding for openjdk21
Matched fields: name
javapackages-local-openjdk21.noarch: Non-essential macros and scripts for Java packaging support
maven-local-openjdk21.noarch: Macros and scripts for Maven packaging support
openjdk-asmtools.noarch: Set of tools used to assemble / disassemble proper and improper Java .class files
openjdk-asmtools7.noarch: Set of tools used to assemble / disassemble proper and improper Java .class files for JDK version 11 and lesser
可能是因为系统版本问题，我使用的Fedora42软件仓库中只能搜索到最新的Java24和Java21，如果仓库中有需要的版本，直接下载即可。当然，如果没有需要的版本，也是有办法安装的，我没怎么用过这种方式，就不献丑了，请自行查找相关资料。以Java21为例，执行以下命令：
sudo dnf install java-21-openjdk-devel -y
将会安装Java编译器和开发所需的工具包，如果只安装 java-xx-openjdk如 sudo dnf install java-21-openjdk -y，只会安装Java运行环境即JRE。简而言之 java-xx-openjdk-devel是JDK，java-xx-openjdk是JRE，JDK包含JRE和开发工具（javadoc（生成 API 文档）、jdb（调试器）、javap（反编译器）等)。
下载完成后，使用以下命令切换默认JDK版本
sudo alternatives --config java
会得到类似下面的输出：
共有 1 个提供“java”的程序。
选项 命令
-----------------------------------------------
*+ 1 /usr/lib/jvm/java-21-openjdk/bin/java
按 Enter 保留当前选项[+]，或者键入选项编号：
输入编号切换即可
下载JDK安装包自行安装
注意，下面的所有路径都要替换为自己系统中的实际路径
首先到Oracle官网下载想要安装的版本，怎么找到下载页面就不说了，直接贴个Java归档页面链接，自行选择需要的版本。
可以选择下载 rpm包使用 dnf安装，会自动配置环境，官方没有提供 deb包，正巧我不怎么用 Debian系的发行版
sudo dnf install /path/to/java.rpm -y
但是我下载的是 tar.gz格式的归档文件，最早学Linux的时候是用的这个，习惯了。
首先查看当前系统已安装的 OpenJDK版本，执行命令：
rpm -qa | grep java
得到类似下面的输出：
tzdata-java-2025b-1.fc42.noarch
javapackages-filesystem-6.4.0-5.fc42.noarch
javascriptcoregtk4.1-2.48.3-1.fc42.x86_64
javascriptcoregtk6.0-2.48.3-1.fc42.x86_64
java-21-openjdk-headless-21.0.7.0.6-2.fc42.x86_64
可以看出目前系统安装的是 OpenJDK21.0.7，卸载当前的 OpenJDK：
sudo rpm -e --nodeps java-21-openjdk-headless-21.0.7.0.6-2.fc42.x86_64
然后将归档文件下载下来，然后执行以下命令解压至你常用的安装软件的目录，我一般放在 /opt/dev目录下。
## 创建目录
sudo mkdir /opt/dev
## 解压文件
sudo tar -xvf ~/下载/Motrix/jdk-8u441-linux-x64.tar.gz -C /opt/dev
解压完成后，配置环境变量，依次执行以下命令：
echo 'export JAVA_HOME=/opt/dev/jdk1.8.0_441' >> /etc/profile
## Fedora 42中profile中已经有export PATH语句，重复export可能会导致系统已有环境变量实效，可以先看一下文件或者直接编辑文件
echo 'PATH=$PATH:$JAVA_HOME/bin' >> /etc/profile
source /etc/profile
验证
安装完成后，执行 java -version即可看到JDK版本已经更换为我们安装的版本
使用dnf这样的软件包管理工具安装的优点在于不用自己下载安装包，安装和环境配置都会自动完成，而且可以很方便的在不同版本之间切换，缺点是想要安装比较就的版本可能不太容易。
手动安装的优点在于可以安装任意版本的JDK，缺点是可能需要自己配置环境