Convert der to jks

JKSBuilder.java

import java.io.ByteArrayInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Hashtable;
import java.util.Map;

public class JKSBuilder {

    private static String defaultAlias = "";
    private static char[] defaultPassword = "".toCharArray();

    public static void main(String[] args) {
        try {
            Map<String, String> argsMap = parseArgs(args);
            PrivateKey key = readRSAkey(argsMap.get("key"));
            Certificate cert = readX509Certificate(argsMap.get("cert"));
            KeyStore keyStore = makeJKS(key, cert);
            keyStore.store(new FileOutputStream(argsMap.get("out")), argsMap.get("password").toCharArray());
        } catch (InvalidKeySpecException | NoSuchAlgorithmException | IOException | CertificateException
                | KeyStoreException e) {
            e.printStackTrace();
        }
    }

    private static KeyStore makeJKS(PrivateKey key, Certificate cert) throws KeyStoreException,
            NoSuchAlgorithmException, CertificateException, IOException {
        KeyStore keyStore = KeyStore.getInstance("JKS");
        keyStore.load(null, defaultPassword);
        keyStore.setKeyEntry(defaultAlias, key, defaultPassword, new Certificate[] { cert });
        return keyStore;
    }

    public static PrivateKey readRSAkey(String keyPath) throws IOException, InvalidKeySpecException,
            NoSuchAlgorithmException {
        return KeyFactory.getInstance("RSA").generatePrivate(
                new PKCS8EncodedKeySpec(Files.readAllBytes(Paths.get(keyPath))));
    }

    public static Certificate readX509Certificate(String certPath) throws CertificateException, IOException {
        return CertificateFactory.getInstance("X.509").generateCertificate(
                new ByteArrayInputStream(Files.readAllBytes(Paths.get(certPath))));
    }

    private static Map<String, String> parseArgs(String[] args) {
        Map<String, String> argsMap = new Hashtable<String, String>();

        for (int i = 0; i < args.length; i += 2) {
            if ("--key".equals(args[i])) {
                argsMap.put("key", args[i + 1]);
            } else if ("--cert".equals(args[i])) {
                argsMap.put("cert", args[i + 1]);
            } else if ("--out".equals(args[i])) {
                argsMap.put("out", args[i + 1]);
            } else if ("--password".equals(args[i])) {
                argsMap.put("password", args[i + 1]);
            }
        }

        return argsMap;
    }

}