Certificate is just a data. You definitely can export it to the file, and import that data into some other file.
If you just want to import one truststore file's data into another, you can directly make use of buffer without storing data into an intermediary file:
keytool.exe -importkeystore -srckeystore %JAVA_HOME%\lib\security\cacerts -destkeystore \your\file\path\filename
-deststoretype jks
-srcstorepass changeit -deststorepass changeit
-v -noprompt
However, you can also do these two operations one by one:
To export the certificate:
keytool -export -alias alias_name -keystore path_to_keystore_file -rfc -file path_to_certificate_file
To import the certificate:
keytool -importcert -alias alias_name -file path_to_certificate_file -keystore truststore_file
More on this can be read here, here and here.