使用Java语言创建一个带公钥的数字证书，并将其安装至本地计算机的代码实现

在Java中，我们可以使用`java.security.cert.X509Certificate`和`KeyPairGenerator`等类来创建数字证书并安装到本地。以下是一个简单的示例，展示如何生成一对密钥对、创建X509证书，以及将证书保存到用户信任store：

import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.cert.X509Certificate;
import java.security.cert.X509CRLEntry;
import java.security.cert.X509v3CertificateBuilder;
import java.util.Date;

import javax.net.ssl.TrustManagerFactory;
import javax.security.auth.x500.X500Principal;
import org.bouncycastle.asn1.x500.X500Name;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import sun.security.x509.CertificateFactory;

// 添加BouncyCastle支持
Security.addProvider(new BouncyCastleProvider());

public class CertificateExample {

    public static void main(String[] args) throws Exception {
        // 初始化密钥对生成器
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
        keyGen.initialize(2048);

        // 生成密钥对
        KeyPair keyPair = keyGen.generateKeyPair();
        PrivateKey privateKey = keyPair.getPrivate();

        // 创建证书颁发者名字
        X500Name caName = new X500Name("CN=My CA");

        // 证书有效期
        Date startDate = new Date();
        Date endDate = new Date(startDate.getTime() + 365 * 24 * 60 * 60 * 1000); // 一年有效期

        // 证书信息
        X509v3CertificateBuilder certBuilder = new JcaX509v3CertificateBuilder(caName,
                BigInteger.valueOf(System.currentTimeMillis()),
                startDate, endDate,
                caName, keyPair.getPublic());

        // 创建自签名的X509证书
        X509Certificate certificate = (X509Certificate) certBuilder.build(privateKey);

        // 将证书保存到文件
        try (FileOutputStream fos = new FileOutputStream("my_certificate.pem")) {
            certificate.save(fos, "PEM");
        }

        // 安装证书到本地truststore
        installCert(certificate);
    }

    private static void installCert(X509Certificate cert) throws IOException, NoSuchAlgorithmException {
        TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509", " SUN");
        tmf.init((java.security.cert.TrustedCertificate[]) null);
        X509TrustManager trustManager = (X509TrustManager) tmf.getTrustManagers()[0];

        CertificateFactory cf = CertificateFactory.getInstance("X.509");
        java.security.cert.Certificate[] certs = {cf.generateCertificate(cert.getEncoded())};
        System.setProperty("javax.net.ssl.trustStore", "path_to_your_truststore.jks"); // 替换为你的truststore路径
        System.setProperty("javax.net.ssl.trustStorePassword", "your_password"); // 替换为你的truststore密码

        // 设置系统默认的信任管理器
        SSLContext sslContext = SSLContext.getInstance("SSL");
        sslContext.init(null, new TrustManager[]{trustManager}, new SecureRandom());
        SSLSocketFactory socketFactory = sslContext.getSocketFactory();
    }
}

请注意，这个例子仅用于演示目的，实际生产环境中你需要处理更多的细节，比如使用真实的CA签发的证书，以及更安全的方式来存储和管理证书。