To import a .cer certificate into a Java keystore, you can use the keytool utility that comes with the Java Development Kit (JDK). The keytool utility is a command-line tool that allows you to manage certificates and keystores.
To trust all certificates when using the Apache HttpClient library to make HTTPS requests, you can create a custom X509TrustManager implementation that trusts all certificates and use it to create an SSLContext with a custom TrustStrategy.