Private jre vs Public jre

今天说一下java环境构建中，jre相关的小知识点。

private jre：一般是C:Program Filesjdk1.8.0jre，必须安装，它为jdk的运行提供必需的环境。

public jre：一般是C:Program FilesJavajre1.8.0，可以选择安装。

如果，平时更新java版本，那么将会在public jre的目录下，添加新版本的jre。有人认为，public jre是多余的，会浪费磁盘空间，对于SSD来说，110M的空间还是很宝贵的，private jre足已。在某些Eclipse集成java版本中，里面就仅使用了private jre，可以应对运行的需求了。

可是，如果有一些java版本的匹配的需求的话，public jre应该就会体现它的作用了。

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官方文档（https://docs.oracle.com/javase/8/docs/technotes/guides/install/windows_jdk_install.html#CHDJCCEG）如下：

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Installing the JDK also installs a private JRE and optionally a public copy. The private JRE is required to run the tools included with the JDK. It has no registry settings and is contained entirely in a jre directory (typically at C:Program Filesjdk1.8.0jre) whose location is known only to the JDK. On the other hand,the public JRE can be used by other Java applications,is contained outside the JDK (typically at C:Program FilesJavajre1.8.0),is registered with the Windows registry (at HKEY_LOCAL_MACHINESOFTWAREJavaSoft),can be removed using Add/Remove Programs,might be registered with browsers,and might have the java.exe file copied to the Windows system directory (which would make it the default system Java platform).

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