1. Java SE 8u11 JRE default installation
----------------------------------------------------------
File used for installation: jre-8u11-windows-i586.exe

C:\> java -version
java version "1.8.0_11"
Java(TM) SE Runtime Environment (build 1.8.0_11-b12)
Java HotSpot(TM) Client VM (build 25.11-b03, mixed mode, sharing)

C:\>
C:\> dir "C:\program files\Java"
 Volume in drive C has no label.
 Volume Serial Number is B4D9-70E6

 Directory of C:\program files\Java

02/10/2015 09:28 AM <DIR> .
02/10/2015 09:28 AM <DIR> ..
02/10/2015 09:29 AM <DIR> jre8
               0 File(s) 0 bytes
               4 Dir(s) 2,903,355,392 bytes free

C:\>

2. Java SE 8u20 JRE default installation
----------------------------------------------------------
File used for installation: jre-8u20-windows-i586.exe

C:\> java -version
java version "1.8.0_20"
Java(TM) SE Runtime Environment (build 1.8.0_20-b26)
Java HotSpot(TM) Client VM (build 25.20-b23, mixed mode)

C:\>
C:\> dir "C:\program files\Java
 Volume in drive C has no label.
 Volume Serial Number is B4D9-70E6

 Directory of C:\program files\Java

02/10/2015 09:50 AM <DIR> .
02/10/2015 09:50 AM <DIR> ..
02/10/2015 09:52 AM <DIR> jre1.8.0_20
               0 File(s) 0 bytes
               4 Dir(s) 1,832,845,312 bytes free

C:\>

3. Java SE 8u31 JRE default installation
----------------------------------------------------------
Files used for installation: jre-8u25-windows-i586.exe, jre-8u31-windows-i586.exe
8u25 was installer prior to 8u31.

C:\> java -version
java version "1.8.0_31"
Java(TM) SE Runtime Environment (build 1.8.0_31-b13)
Java HotSpot(TM) Client VM (build 25.31-b07, mixed mode, sharing)

C:\> dir "C:\Program files\Java"
 Volume in drive C has no label.
 Volume Serial Number is B4D9-70E6

 Directory of C:\Program files\Java

02/10/2015 10:12 AM <DIR> .
02/10/2015 10:12 AM <DIR> ..
02/10/2015 10:05 AM <DIR> jre1.8.0_25
02/10/2015 10:13 AM <DIR> jre1.8.0_31
               0 File(s) 0 bytes
               5 Dir(s) 770,367,488 bytes free

C:\>
C:\> "C:\Program files\Java\jre1.8.0_25\bin\java.exe" -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b18)
Java HotSpot(TM) Client VM (build 25.25-b02, mixed mode)

C:\>

4. Comments
-------------------
Expected behaviour is reproduced with 8u11:
The software was installed into directory 'jre8' (patch-in-place).
Beginning with 8u20, the behaviour changed unexpectedly.
The software was installed into directory 'jre1.8.0_20' (static).
Unexpected behaviour is still reproducible with 8u31 (most recent software released).
The software was installed into directory 'jre1.8.0_31' (static).
Previous (static) installation was not removed.