What is the difference between jre folder under JDK folder and jre folder?

Question

• NOTE: The question is not about the difference between JDK and JRE.

Oh, I am sorry. The question is not discuss about JDK and JRE. But I cannot express clearly in my title. So I try to explain in here.

I want to know the difference between two folders!

C:\\Program Files\\Java\\jdk1.8.0_161\\jre and C:\\Program Files\\Java\\jre1.8.0_161

Describe in details:

I am new to JAVA. I have installed the JDK in my Windows 10. When I install jdk, there were two steps. After double click jdk-8u161-windows-x64.exe , two steps as follows:

1. Step 1: install jdk. (In C:\\Program Files\\Java\\jdk1.8.0_161 )

2. Step 2: install jre. (In C:\\Program Files\\Java\\jre1.8.0_161 )

But when I open the jdk1.8.0_161 folder. I can also find a jre folder.

Could anyone tell me the difference between C:\\Program Files\\Java\\jdk1.8.0_161\\jre and C:\\Program Files\\Java\\jre1.8.0_161 ?

If they are the same, why is jre installed in the installation process of jdk ? Are they duplicated?
In other world, is Step 2 needless?

Answer 1

The JRE within the JDK C:\\Program Files\\Java\\jdk1.8.0_161\\jre (also referenced as private JRE) is used by the JDK tools. The JRE outside C:\\Program Files\\Java\\jre1.8.0_161 (also referenced as the public JRE) should is meant to be used by the Java applications.

private JRE

• contains the library (attach.dll) needed for the use of the attach API
• will be uninstalled with the JDK

public JRE

• registers the Java Plug-in and the java web start in the browsers
• this JRE is registered in the system, eg as runtime for Java applications, the Java control panel
• can be uninstalled separately from JDK