curl --cert client.cert.pem --key client.key.pem ...

final char[] JKS_PASSWORD = "password".toCharArray();

SSLContext sslContext = SSLContexts.custom().loadTrustMaterial(
    new File("ssl/keystore.jks"), JKS_PASSWORD, new TrustSelfSignedStrategy()).build();

HttpClient httpsClient = HttpClients.custom().setSSLContext(sslContext).build();
HttpResponse rResponse = httpsClient.execute(new HttpGet(MY_URL));

java.lang.NoSuchMethodError: org.apache.http.impl.client.HttpClientBuilder.setSSLContext(Ljavax/net/ssl/SSLContext;)Lorg/apache/http/impl/client/HttpClientBuilder;

...

SSLConnectionSocketFactory sslSocketFactory = new SSLConnectionSocketFactory(
        sslContext,
        new String[] { "TLSv1", "TLSv1.1", "TLSv1.2" },
        null,
        SSLConnectionSocketFactory.getDefaultHostnameVerifier());


HttpClient httpsClient = HttpClients.custom().setSSLSocketFactory(sslSocketFactory).build();
HttpResponse rResponse = httpsClient.execute(new HttpGet(MY_URL));

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

String keyPhrase = "your_key_there";

KeyStore keyStore = KeyStore.getInstance("PKCS12");
keyStore.load(getClass().getClassLoader().getResourceAsStream("your_cert"), keyPhrase
  .toCharArray());

SSLContext sslContext = SSLContexts.custom().loadKeyMaterial(keyStore, keyPhrase.toCharArray()).build();

HttpGet httpGet = new HttpGet("your_url_there");

HttpClient httpClient = HttpClients.custom().setSSLContext(sslContext).build();
HttpResponse response = httpClient.execute(httpGet);