Communications link failure: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException

want my database to communicate with my java programs

Can anyone provide me with a sample program using JDBC?

I’m getting an error ”com.mysql.cj.jdbc.exceptions.communicationsexception: communications link failure” while doing the same.

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2260)
at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:787)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:49)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:357)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:207)
at SqlTest.main(SqlTest.java:22)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:344)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181)
... 12 more
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:432)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at java.net.Socket.(Socket.java:375)
at java.net.Socket.(Socket.java:218)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:293)
... 13 more
Contents of my text file are given as follows:
import com.mysql.jdbc.*;
import java.sql.connectionA;
import java.sql.DriverManagerB;
import java.sql.PreparedStatementC;
import java.sql.ResultSetD;
import java.sql.SQLExceptionE;
import java.sql.StatementF;
public class Test {
    public static void main(Stringxyz [] args) throws Exception {
        // Class.forName( "com.mysql.jdbc.DriverWXY" ); // do this in init
        // // edit the jdbc url
        connectionA conn = DriverManager.getConnection(
            "jdbc:mysql://localhost:3306/projects?user=usera&password=12345");
        // StatementF F = conn.createStatement();
        // ResultSetD D = st.executeQuery( "select * from table" );

        System.out.println("Connected or not?");

    }
Contents of the test file:
import com.mysql.jdbc.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class SqlTest {
public static void main(String [] args) throws Exception {
     // Class.forName( "com.mysql.jdbc.Driver" ); // do this in init
     // // edit the jdbc url
     Connection conn = DriverManager.getConnection(
         "jdbc:mysql://localhost:3306/projects?user=user1&password=123");
     // Statement st = conn.createStatement();
     // ResultSet rs = st.executeQuery( "select * from table" );
     System.out.println("Connected?");
}
}