Get default trust materia #javax-ssl-truststore

tm.java

import java.security.KeyStore;
import java.security.cert.X509Certificate;

import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
tmf.init((KeyStore) null);
for (TrustManager tm : tmf.getTrustManagers()) {
    if (tm instanceof X509TrustManager) {
        X509TrustManager xtm = (X509TrustManager) tm;
        for (X509Certificate x509c : xtm.getAcceptedIssuers()) {
            System.out.println(x509c.getSubjectX500Principal().getName());
        }
    }
}