To recreate P1.jar/P2.jar, although I doubt this will ever be necessary, do
the following.

mkdir classes
javac -d classes \
    P1SecretKeyFactory.java Provider1.java \
    P2SecretKeyFactory.java Provider2.java

cd classes
jar -cvf ../P1.jar com/p1
jar -cvf ../P2.jar com/p2
cd ..
rm -rf classes

jarsigner -keystore YourJCESigningKeyKeyStore.ks P1.jar yourKeySigningAlias
jarsigner -keystore YourJCESigningKeyKeyStore.ks P2.jar yourKeySigningAlias