#264: switch from AssertionError to IllegalStateException (see https:…

…//stackoverflow.com/questions/62360207/as-a-library-designer-should-i-avoid-assertionerrors-and-throw-exceptions-inste#comment110292742_62360207)

modules/core-module/src/main/java/org/simplejavamail/api/mailer/config/TransportStrategy.java

@@ -173,7 +173,7 @@ public String propertyNameSSLTrust() {
 		 */
 		@Override
 		public String propertyNameCheckServerIdentity() {
-			throw new AssertionError("This property is not relevant for plain SMTP");
+			throw new IllegalStateException("This property is not relevant for plain SMTP");
 		}
 
 		/**

modules/core-module/src/main/java/org/simplejavamail/internal/util/CertificationUtil.java

@@ -36,7 +36,7 @@ public static X509Certificate readFromPem(InputStream pemData)
 				Class<Provider> bouncyCastleClass = (Class<Provider>) forName(BOUNCY_CASTLE_PROVIDER_CLASS);
 				Security.addProvider(getProvider(bouncyCastleClass));
 			} catch (ClassNotFoundException e) {
-				throw new AssertionError(format("Class found but also not found??? (%s)", BOUNCY_CASTLE_PROVIDER_CLASS));
+				throw new IllegalStateException(format("Class found but also not found??? (%s)", BOUNCY_CASTLE_PROVIDER_CLASS));
 			}
 		} else {
 			throw new SmimeSupportMissingException();

modules/core-module/src/main/java/org/simplejavamail/internal/util/SimpleConversions.java

@@ -39,7 +39,7 @@ public static Boolean convertToBoolean(@Nullable final Object value) {
 			} else if (strValue.equalsIgnoreCase("false") || strValue.equalsIgnoreCase("0")) {
 				return false;
 			}
-			throw new AssertionError("Wrong property must have been requested");
+			throw new IllegalArgumentException("Wrong property must have been requested");
 		}
 	}
 }

modules/simple-java-mail/src/main/java/org/simplejavamail/converter/EmailConverter.java

@@ -428,7 +428,7 @@ public static MimeMessage emailToMimeMessage(@NotNull final Email email, @NotNul
 			return MimeMessageProducerHelper.produceMimeMessage(checkNonEmptyArgument(email, "email"), checkNonEmptyArgument(session, "session"));
 		} catch (UnsupportedEncodingException | MessagingException e) {
 			// this should never happen, so we don't acknowledge this exception (and simply bubble up)
-			throw new AssertionError(e.getMessage(), e);
+			throw new IllegalStateException(e.getMessage(), e);
 		}
 	}
 
@@ -510,7 +510,7 @@ public static String mimeMessageToEML(@NotNull final MimeMessage mimeMessage) {
 			return os.toString(UTF_8.name());
 		} catch (IOException | MessagingException e) {
 			// this should never happen, so we don't acknowledge this exception (and simply bubble up)
-			throw new AssertionError("This should never happen", e);
+			throw new IllegalStateException("This should never happen", e);
 		}
 	}
 

modules/simple-java-mail/src/main/java/org/simplejavamail/converter/internal/mimemessage/MimeMessageProducer.java

@@ -57,7 +57,7 @@ public String toString() {
 				try {
 					return "MimeMessage<id:" + super.getMessageID() + ", subject:" + super.getSubject() + ">";
 				} catch (MessagingException e) {
-					throw new AssertionError("should not reach here");
+					throw new IllegalStateException("should not reach here");
 				}
 			}
 		};

modules/simple-java-mail/src/main/java/org/simplejavamail/converter/internal/mimemessage/MimeMessageProducerHelper.java

@@ -40,6 +40,6 @@ public static MimeMessage produceMimeMessage(@NotNull Email email, @NotNull Sess
 				return mimeMessageProducer.populateMimeMessage(email, session);
 			}
 		}
-		throw new AssertionError("no compatible MimeMessageProducer found for email");
+		throw new IllegalStateException("no compatible MimeMessageProducer found for email");
 	}
 }

modules/simple-java-mail/src/main/java/org/simplejavamail/internal/modules/ModuleLoader.java

@@ -68,7 +68,7 @@ public static SMIMEModule loadSmimeModule() {
 
 	public static BatchModule loadBatchModule() {
 		if (FORCED_DISABLED_MODULES.contains(BatchModule.class)) {
-			throw new AssertionError("BatchModule forcefully disabled");
+			throw new IllegalStateException("BatchModule forcefully disabled");
 		}
 		if (!LOADED_MODULES.containsKey(BatchModule.class)) {
 			LOADED_MODULES.put(BatchModule.class, loadModule(

modules/simple-java-mail/src/main/java/org/simplejavamail/mailer/internal/MailerImpl.java

@@ -319,7 +319,7 @@ public final AsyncResponse sendMail(final Email email, @SuppressWarnings("SamePa
 						.executeAsync(operationalConfig.getExecutorService(), "sendMail process", sendMailClosure);
 			}
 		}
-		throw new AssertionError("Email not valid, but no MailException was thrown for it");
+		throw new IllegalStateException("Email not valid, but no MailException was thrown for it");
 	}
 
 	/**