(0x0000274D/10061) Is the server running on host and accepting TCP/IP connections on port 5432? code example

Example 1: could not connect to server: Connection refused Is the server running on host and accepting TCP/IP connections on port 5432?

cd /etc/postgresql/9.x/main/
------- open file named postgresql.conf
sudo nano postgresql.conf
------- add this line to that file
listen_addresses = '*'
------- then open file named pg_hba.conf
sudo nano pg_hba.conf
------- and add this line to that file
host  all  all 0.0.0.0/0 md5
------- restart your server
sudo /etc/init.d/postgresql restart

Example 2: [08001] Connection to localhost:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections. java.net.ConnectException: Connection refused: connect.

org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.