JDK21安装配置全攻略

以下是JDK 21的安装与配置详细教程，按照操作系统分类说明：

一、Windows系统安装

下载JDK 21
- 访问Oracle官网JDK下载页面
- 选择"JDK 21" → Windows版本（推荐x64 MSI Installer）

安装步骤

# 双击下载的.msi文件
# 按向导提示操作，建议使用默认安装路径：
C:\Program Files\Java\jdk-21\

配置环境变量
- 打开系统设置 → 高级系统设置 → 环境变量
- 新建系统变量：
```
变量名：JAVA_HOME
变量值：C:\Program Files\Java\jdk-21
```
- 编辑Path变量，新增两条：
```
%JAVA_HOME%\bin
%JAVA_HOME%\jre\bin
```
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二、macOS系统安装

下载JDK 21
- 官网选择macOS .dmg安装包（ARM64或x64）

安装过程

# 双击.dmg文件 → 运行安装包
# 默认安装路径：
/Library/Java/JavaVirtualMachines/jdk-21.jdk

配置环境变量

打开终端，编辑配置文件：
```
nano ~/.zshrc  # 或 ~/.bash_profile
```

添加：

export JAVA_HOME=$(/usr/libexec/java_home -v 21)
export PATH=$JAVA_HOME/bin:$PATH

生效配置：
```
source ~/.zshrc
```

三、Linux系统安装（Ubuntu示例）

下载.tar.gz包

wget https://download.oracle.com/java/21/latest/jdk-21_linux-x64_bin.tar.gz

解压安装

sudo tar -xvzf jdk-21_linux-x64_bin.tar.gz -C /usr/lib/jvm/

配置环境

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk-21/bin/java 1
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk-21/bin/javac 1

四、验证安装

所有系统通用验证命令：

java -version
# 应显示：java version "21" ...
javac -version
# 应显示：javac 21

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