Java. SQL. sqlexception: Io exception: the network adapter cocould not establish the connection

Io exception: the network adapter cocould not establish the connection
This exception usually occurs when the database is related to your PC settings.

This exception occurs in the following ways:

1. IP address error.
URL setting error, for example: JDBC: oracle: thin: @ 192.168.0.36: 1521: sharp
Incorrect database server: ping the Server IP address. Incorrect. Change the URL to correct
Port Number error: it is normal.
Perform the following operations: Type sqlplus on DOS and check whether oracle is enabled.
1, but it is normal. Execute Step 1 below.

2. Firewall
If a firewall is installed on the machine, it may be caused by blocking the server port number. Close the firewall and try again.
Still not working. Execute step 1.

3. The ImagePath value in the Registry on the PC is not modified when the Database Listener is not started.
The following uses the current mainstream database oracle as an example.
Restart the Database Listener manually

4. You cannot use 127.0.0.1 or localhost.