Oracle Network Adapter could not establish the connection tips

Question: 
I am trying to install SQL Developer and when I try to open
the forst screen and connect I get this network adapter error:

java.sql.SQLException: Io
exception: The Network Adapter could not establish the connection.

How do I resolve this

Network Adapter could not establish the connection error?

Answer:  Whenever you see
a

Network Adapter could not establish the connection, you have either
the wrong SQL Developer URL or you have a basic SQL*Net
connectivity issue!  This error is most likely caused by one of
these factors:

– You are using the wrong URL

– The wrong
port number or IP address (or DNS host name) was used

– The
listener is not configured properly

– The listener process
(service) is not running.  You can re-start it with the
“lsnrctl start” command or on Windows by starting the listener
service.

For a step by step checklist, see my notes on

troubleshooting an Oracle connection problem.

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