Extract certificate from JKS in PEM format

Main.java

package org.example;

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openssl.jcajce.JcaPEMWriter;
import org.bouncycastle.util.io.pem.PemObject;

import java.io.*;
import java.security.Key;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.Security;
import java.security.cert.Certificate;

public class Main {
    public static final String jksPassword = "password";
    public static final String jksPath = "/Users/oofnivek/Desktop/keystore.jks";
    public static final String entryAlias = "example.org";

    public static void main(String[] args) {
        Security.addProvider(new BouncyCastleProvider());

        KeyStore keyStore = null;
        try {
            keyStore = KeyStore.getInstance("JKS");
        } catch (KeyStoreException e) {
            throw new RuntimeException(e);
        }
        try (FileInputStream fileInputStream = new FileInputStream(jksPath)) {
            keyStore.load(fileInputStream, jksPassword.toCharArray());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

        Key key = null;
        try {
            key = keyStore.getKey(entryAlias, jksPassword.toCharArray());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }

        // extracting private key
        try (JcaPEMWriter jcaPEMWriter = new JcaPEMWriter(new FileWriter("private_key.pem"))) {
            jcaPEMWriter.writeObject(new PemObject("PRIVATE KEY", key.getEncoded()));
            System.out.println("Private key successfully extracted");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        Certificate certificate = null;
        try {
            certificate = keyStore.getCertificate(entryAlias);
        } catch (KeyStoreException e) {
            throw new RuntimeException(e);
        }

        // extracting certificate
        try(JcaPEMWriter jcaPEMWriter = new JcaPEMWriter(new FileWriter("certificate.pem"))){
            jcaPEMWriter.writeObject(certificate);
            System.out.println("Certificate successfully extracted");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        // extract public key
        try(JcaPEMWriter jcaPEMWriter = new JcaPEMWriter(new FileWriter("public_key.pem"))){
            jcaPEMWriter.writeObject(new PemObject("PUBLIC KEY", certificate.getPublicKey().getEncoded()));
            System.out.println("Public key successfully extracted");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}