You can extract the JDK folder from the Installation EXE.

Check this link for the steps. The post was for JDK 1.7 it will work for JDK 1.8 also

Do the following.

Steps

1. Download JDK from Oracle
2. Download and Install 7-zip from here
3. Open installition exe using 7-Zip
4. Extract the tools.zip
5. Extract the content of tools.zip to a folder (e.g. c:\jdk).
6. Open the extracted folder in cmd prompt.
7. Execute for /r %x in (*.pack) do .\bin\unpack200 -r "%x" "%~dx%~px%~nx.jar" command
8. Set JAVA_HOME to the jdk (e.g c:\jdk) folder.
9. Add %JAVA_HOME%/bin to the PATH env variable.

Testing

Run the following command to check the installation, it will print the version of JDK.

c:> javac -version
javac 1.7.0_51

NOTE: Tested with JDK 1.7 and 1.8

Update 1

Edited the answer to add the steps in the answer itself instead of the link to a blog post.

Update 2

For 64-Bit please check unpack-jdk-x64.bat by grabantot

Stewardship

Be aware that Oracle stopped providing free-of-cost security updates to Java 8. See Oracle Java SE Support Roadmap.

Red Hat (IBM) has taken stewardship of the OpenJDK 8 & OpenJDK 11 LTS releases.

Oracle branded

Oracle JDK 8 Update 221 is available here. Be sure to read the terms of the license, and be aware of their intention towards further updates.

OpenJDK

The open-source distributions based on OpenJDK are available from various vendors.

The first that comes to mind is AdoptOpenJDK.net, providing Java 8 with Update 282 currently.

Amazon provides OpenJDK 8 in their Corretto offering. Especially suitable if you deploy to AWS.

Zulu by Azul Systems also provides OpenJDK 8, certified as Java. They offer optional support plans as well.

See the nifty diagram I made for sourcing Java 11. Some of those same vendors also provide Java 8, with and without paid support.