Executing a query with JDBC Postgresql gives error: 'org.postgresql.util.PSQLException: ERROR: relation "clientes" does not exist'

Question

This error happens when executing any query in a table (Clientes).

package database;
import java.sql.*;
import java.util.Properties;

// Database Access Object
public class ClienteDao {
    private Connection conexion = null;
    public void conectar () {
        String baseDeDatos = "pruebaLucas";
        String usuario = "postgres";
        String pass = "contra31";
        String host = "localhost";
        String puerto = "5432";
        String driver = "org.postgresql.Driver";
        String conexionUrl = "jdbc:postgresql://" + host + ":" + puerto + "/" + baseDeDatos +
                "?user=" + usuario + "&password=" + pass + "&ssl=false";

        try {
            Properties props = new Properties();
            props.setProperty("currentSchema", "schema_luki");
            Class.forName(driver);
            this.conexion = DriverManager.getConnection(conexionUrl, props);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private String construirQueryAgregarCliente (String cNombre, String cApellido, String cTel, String cEmail) {
        return String.format(
                "INSERT INTO Clientes (nombre, apellido, telefono, email)" + "VALUES (%s, %s, %s, %s);",
                cNombre, cApellido, cTel, cEmail);
    }

    private void ejecutarQuery (String q) {
        if (this.conexion != null) {
            try {
                Statement statement = this.conexion.createStatement();
                statement.executeQuery(q);
                statement.close();
            } catch (SQLException e) {
                throw new RuntimeException(e);
            }

        }
    }

    public void agregarCliente (String nombre, String apellido, String telefono, String email) {
        this.ejecutarQuery( this.construirQueryAgregarCliente(nombre, apellido, telefono, email) );
    }


}

I execute agregarCliente(...) in a form (button click) and I get the error:

Exception in thread "AWT-EventQueue-0" java.lang.RuntimeException: org.postgresql.util.PSQLException: ERROR: relation "clientes" does not exist
  Position: 13
    at database.ClienteDao.ejecutarQuery(ClienteDao.java:41)
    at database.ClienteDao.agregarCliente(ClienteDao.java:48)
    at businessLogic.ManejadorClientes.agregarCliente(ManejadorClientes.java:15)
    at frontend.DataForm$1.actionPerformed(DataForm.java:49)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
    at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
    at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
    at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
    at java.desktop/java.awt.Component.processMouseEvent(Component.java:6626)
    at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3389)
    at java.desktop/java.awt.Component.processEvent(Component.java:6391)
    at java.desktop/java.awt.Container.processEvent(Container.java:2266)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5001)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2324)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4833)
    at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4948)
    at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4575)
    at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4516)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2310)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2780)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4833)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:722)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:716)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:97)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:746)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:744)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:743)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

This is the structure of the Data base that I'm using (pruebaLucas):

How can I fix this problem? The connection look fine, It's something with the query.