Download NetBeans: http://netbeans.apache.org/download/nb120/nb120.html
make file executable

$ chmod +x Apache-NetBeans-12.0-bin-linux-x64.sh

Run it and get an error

$ ./Apache-NetBeans-12.0-bin-linux-x64.sh 
Configuring the installer...
Searching for JVM on the system...
Extracting installation data...
Running the installer wizard...

Exception: java.awt.HeadlessException thrown from the UncaughtExceptionHandler in thread "main"

Everything you need is proper Java. 
You can try to install java openjdk from Fedora repo, but it won't help.

dnf install java-latest-openjdk

So you need to download Java JDK from Oracle
https://jdk.java.net/
 

# wget https://download.java.net/java/GA/jdk14.0.1/664493ef4a6946b186ff29eb326336a2/7/GPL/openjdk-14.0.1_linux-x64_bin.tar.gz
# tar -zxvf openjdk-14.0.1_linux-x64_bin.tar.gz
# mkdir /usr/java
# cp jdk-14.0.1 /usr/java

The only thing you need to do is make this java default.
For this purpose you have /etc/alternatives
 

# ln -s /usr/java/jdk-14.0.1/bin/java /etc/alternatives/java
# ln -s /usr/java/jdk-14.0.1 /etc/alternatives/jdk-14.0.1

Now you can run NetBeans installation.