无需下载证书即可连接 Java 和 HTTPS URL

此代码连接到HTTPS站点，我假设我没有验证证书。但是，为什么我不必在本地为站点安装证书呢？难道我不必在本地安装证书并为此程序加载它，还是将其下载到幕后？客户端到远程站点之间的流量在传输过程中是否仍加密？

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;
import java.security.cert.X509Certificate;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

public class TestSSL {

    public static void main(String[] args) throws Exception {
        // 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
        final 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);

        URL url = new URL("https://www.google.com");
        URLConnection con = url.openConnection();
        final Reader reader = new InputStreamReader(con.getInputStream());
        final BufferedReader br = new BufferedReader(reader);        
        String line = "";
        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }        
        br.close();
    } // End of main 
} // End of the class //