import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.Key;
import java.security.KeyStore;
import java.security.cert.Certificate;
public class Main {
public static void main(String[] argv) throws Exception {
FileInputStream is = new FileInputStream("your.keystore");
KeyStore keystore = KeyStore.getInstance(KeyStore.getDefaultType());
keystore.load(is, "my-keystore-password".toCharArray());
String alias = "myalias";
char[] password = "password".toCharArray();
Certificate cert = keystore.getCertificate(alias);
File keystoreFile = new File("your.keystore");
// Load the keystore contents
FileInputStream in = new FileInputStream(keystoreFile);
keystore.load(in, password);
in.close();
// Add the certificate
keystore.setCertificateEntry(alias, cert);
// Save the new keystore contents
FileOutputStream out = new FileOutputStream(keystoreFile);
keystore.store(out, password);
out.close();
}
}