Using the PlaceHolder project: Failed to build apk.

First time trying to do an Android build set up, so I am very open to the possibility that I did something stupid.
I am following these instructions:

TL;DR: I followed the steps, and I am using the Unity Placeholder Project to test out the Android APK generation process, but I am running into many problems.

Here’s what I have:
Unity Version 5.6.3p3
A Moto G4 Play w/Android 6.0.1 attached via USB
jdk-9.0.1_windows-x64_bin.exe (JDK)
PC SDK version:

- I had a similar issue to: unable to list target platform - Questions & Answers - Unity Discussions
So I downrevved “tools” to 25.2.5 like they suggested, which did clear the other issue, but now I have this:

CommandInvokationFailure: Failed to build apk.
C:/Program Files/Java/jdk-9.0.1\bin\java.exe -Xmx2048M -Dcom.android.sdkmanager.toolsdir=“C:/Users/Roger/AppData/Local/Android/Sdk\tools” -Dfile.encoding=UTF8 -jar “C:\Program Files\Unity\Editor\Data\PlaybackEngines\AndroidPlayer/Tools\sdktools.jar” -

stderr[
Exception in thread “main” java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at SDKMain.main(SDKMain.java:130)
Caused by: java.lang.NoClassDefFoundError: sun/misc/BASE64Encoder
at com.android.sdklib.internal.build.SignedJarBuilder.(SignedJarBuilder.java:177)
at com.android.sdklib.build.ApkBuilder.init(ApkBuilder.java:446)
at com.android.sdklib.build.ApkBuilder.(ApkBuilder.java:422)
at com.android.sdklib.build.ApkBuilder.(ApkBuilder.java:362)
at UnityApkBuilder.(UnityApkBuilder.java:214)
at UnityApkBuilder.main(UnityApkBuilder.java:34)
… 5 more
Caused by: java.lang.ClassNotFoundException: sun.misc.BASE64Encoder
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:563)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)
… 11 more
]
stdout[

]
exit code: 1
UnityEditor.Android.Command.Run (System.Diagnostics.ProcessStartInfo psi, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
UnityEditor.Android.AndroidSDKTools.RunCommandInternal (System.String javaExe, System.String sdkToolsDir, System.String[ ] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
UnityEditor.Android.AndroidSDKTools.RunCommandSafe (System.String javaExe, System.String sdkToolsDir, System.String[ ] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg)
UnityEditor.BuildPlayerWindow:BuildPlayerAndRun()

OK I solved the issue, thanks to a friend.
Due to this issue: http - java.lang.NoClassDefFoundError: sun/misc/BASE64Encoder - Stack Overflow

You can’t use those classes, so I downgraded to Java SE Dev Kit 8u152 and success.