Unable to find valid certification path to requested target, trying to use a SMS api via https request

I'm trying to send a SMS from java using an API.

I just need to make an https request with parameters written in the URL.

https://notificame.claro.com.hn/api/http/send_to_contact?msisdn504999999=&message=mymessage&api_key=00000&id=000

If I copy the resulting url and paste it directly on my browser, it sends the SMS.

I have a working code using this on PHP, but I need it working on JAVA

I've tried this:

try 
    {
        HttpsURLConnection con;
        URL url = new URL(pre_url); 
        con = (HttpsURLConnection) url.openConnection();
        System.out.println(url.getContent());

    } catch (MalformedURLException ex) {
        Logger.getLogger(crearUsuarioBean.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(crearUsuarioBean.class.getName()).log(Level.SEVERE, null, ex);
    }

but Im getting this error:

Severe:   javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1949)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:302)...

I also followed some instructions using keytool to add the certificate with .cer to cacerts but had no success. I have two folders, jdk1.8.0_131 and jre1.8.0_131, so I tried installing the certificate on both already. Still no success.

This is the code that makes the job for me on PHP:

function enviarMensaje($cel, $solicitud, $id){     
$mensaje="My message";
$url = "https://notificame.claro.com.hn/api/http/send_to_contact?msisdn=504".$cel."&message=".$mensaje."&api_key=MyAppiKey&id=".$id;
$url = str_replace(" ", "%20", $url);
file($url);
echo $url."<br />\n";   

}

I just need something simple like this.
Im working on JSF2.2 using Primefaces

Or maybe some way to call a simple php code directly from java.

Help please.

After days with the same problem I finally got a solution that might work for some of you.

The trick is to create a TrustManager, that way it can ignore all the SSL stuff.

I added this code:

// Create a trust manager that does not validate certificate chains
    TrustManager[] trustAllCerts = new TrustManager[] {new X509TrustManager() {
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return null;
            }
            public void checkClientTrusted(X509Certificate[] certs, String authType) {
            }
            public void checkServerTrusted(X509Certificate[] certs, String authType) {
            }
        }
    };

    // Install the all-trusting trust manager
    SSLContext sc = SSLContext.getInstance("SSL");
    sc.init(null, trustAllCerts, new java.security.SecureRandom());
    HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());

    // Create all-trusting host name verifier
    HostnameVerifier allHostsValid = new HostnameVerifier() {
        public boolean verify(String hostname, SSLSession session) {
            return true;
        }
    };

    // Install the all-trusting host verifier
    HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);

after this any connection made to an HTTPS url will work.

I found the solution here:
https://nakov.com/blog/2009/07/16/disable-certificate-validation-in-java-ssl-connections/