Java Install

mac

brew install java11 # openjdk

# For the system Java wrappers to find this JDK, symlink it with
  sudo ln -sfn /opt/homebrew/opt/openjdk@11/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-11.jdk

# If you need to have openjdk@11 first in your PATH, run:
  echo 'export PATH="/opt/homebrew/opt/openjdk@11/bin:$PATH"' >> ~/.zshrc

# For compilers to find openjdk@11 you may need to set:
  export CPPFLAGS="-I/opt/homebrew/opt/openjdk@11/include"

ubuntu

# ubuntu
sudo apt install openjdk-8-jdk  # openjdk-11-jdk

java -version # 查看默认版本

sudo update-alternatives --config java  # 安装了多个Java版本，修改默认版本

sudo apt remove openjdk-8-jdk # 删除

# 推荐：vscode command shift p 输入：jdk，选择安装即可

# 查看javahome位置
/usr/libexec/java_home -V

推荐配置 JAVA_HOME

JAVA_HOME：指向 JDK 的安装目录，Eclipse/NetBeans/Tomcat 等软件就是通过搜索 JAVA_HOME 变量来找到并使用安装好的 JDK.

将 export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64 写入 ~/.zshrc 即可完成配置

java for vscode

vscode 读取 JDK 的顺序如下：

• settings.json 文件中的 java.home 配置

此配置可能已过时，待笔者确认后修改

# ubuntu 通过命令 sudo update-alternatives --config java 获取JDK安装路径
{
    "java.home":"/usr/lib/jvm/java-11-openjdk-amd64",
    "java.configuration.runtimes": [
        {
            "name": "JavaSE-1.8",
            "path": "/usr/lib/jvm/java-8-openjdk-amd64",
            "default": true
        },
        {
            "name": "JavaSE-11",
            "path": "/usr/lib/jvm/java-11-openjdk-amd64",
        },
    ]

}

• the JDK_HOME environment variable
• the JAVA_HOME environment variable
• on the current system path