Thank you, Mara. It's a good suggestion. I didn't notice before.
I will paste the text here and hope someone else will help me.
I encountered a problem when I am running the last code of part 3 jenv add /Library/Java/JavaVirtualMachines/jdk1.8.0_162.jdk/Contents/Home oracle64-1.8.0_162 added
I already found the path on my computer,
wireless-10-105-238-245:~ jingsixu$ ls -l `which java`
lrwxr-xr-x 1 root wheel 74 Mar 28 05:53 /usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java
However, this path didn't work.
wireless-10-105-238-245:~ jingsixu$ jenv add /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java
/System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java is not a valid path to java installation
wireless-10-105-238-245:~ jingsixu$ oracle64-1.8.0_162 added
-bash: oracle64-1.8.0_162: command not found
wireless-10-105-238-245:~ jingsixu$ jenv add /Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java
/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java is not a valid path to java installation
wireless-10-105-238-245:~ jingsixu$ oracle64-1.8.0_162 added