{code}
HttpURLConnection connection = null;
        try
        {
            connection = (HttpURLConnection) new URL(url).openConnection();
            connection.setReadTimeout(1500);
            connection.setConnectTimeout(3000);
            connection.setRequestMethod("HEAD");
            connection.setDoInput(true);

            int responseCode = connection.getResponseCode();

            boolean isHealthy = responseCode / 100 == 2;

            Date certificateExpiration = null;

            
            if (connection instanceof HttpsURLConnection)
            {
                try
                {
                    Certificate[] certs = ((HttpsURLConnection) connection).getServerCertificates();
                    if (certs != null && certs.length > 0 && certs[0] instanceof X509Certificate)
                    {
                        certificateExpiration = ((X509Certificate) certs[0]).getNotAfter();
                    }
                }
                catch (SSLPeerUnverifiedException e)
                {
                    System.err.println("Error getting server certificates: " + e.getMessage());
                }
            }
            // Consume the input stream to release the connection back to the pool
            try (InputStream inputStream = connection.getInputStream())
            {
                // Do nothing, just consume the stream
            }
            catch (IOException e)
            {
                // Ignore, we've already got the response code
            }

            // If there's an error stream, consume it to release the connection
            try (InputStream errorStream = connection.getErrorStream())
            {
                // Do nothing, just consume the stream
            }
            catch (Exception e)
            {
                System.err.println("Error consuming error stream: " + e.getMessage());
            }

            System.out.println("Healthy: " + isHealthy + " Code: " + responseCode + " Cert expiration: " + certificateExpiration);
        }
        catch (Exception e)
        {
            System.err.println("Error checking health: " + e.getMessage());
        }
{code}

Fails (on an https url) when trying to get the server certificates:

{code}
java.lang.IllegalStateException: connection not yet open
at java.base/sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getServerCertificates(AbstractDelegateHttpsURLConnection.java:274)
at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getServerCertificates(HttpsURLConnectionImpl.java:212)
at Test.checkHealth(Test.java:36)
at Test.main(Test.java:85)
{code}

Adding an explicit call to connect() prior to callin getServerCertificates allows it to succeed, but causes file handle leaks.