为什么在安装Java的同时安装两个JRE

Question

I installed jdk 1.8. While installing, two JRE were copied to my computer:

The first is inside JDK folder and the second is outside .What's the purpose of having two JRE in the same Operating System .

Isn't one JRE enough to handle all requests .

Answer 1

Private vs. public JRE - Installing the JDK installs a private Java SE Runtime Environment (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 Files\\jdk1.6.0\\jre) 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 Files\\Java\\jre1.6.0), is registered with the Windows registry (at HKEY_LOCAL_MACHINE\\SOFTWARE\\JavaSoft), can be removed using Add/Remove Programs, might or might not be registered with browsers, and might or might not have java.exe copied to the Windows system directory (making it the default system Java platform or not).

Source: http://www.oracle.com/technetwork/java/javase/install-windows-189425.html

Answer 2

浏览器将从java / jre运行，Java从java / jdk / jre运行，当我们安装Internet Explorer时，它将下载jre JDK / jre，它将被命令行工具使用，因为命令行默认的Java home会设置为jdk，它会查找jre并在jdk / jre中运行java.exe