Taking a cue from the Java API best practices from the revered book 'Effective Java' by Joshua Bloch, I am going to use the Builder pattern[Chapter 2, Item 2] instead of creating one method with a long list of (mostly optional) parameters. This pattern also simulates named optional parameters as found in Ada and Python. As a implementer, it gives us the flexibility to add new parameters without breaking the existing use of it's methods. Another advantage of the Builder pattern is that the developer using this util class/method doesn't need to remember the order of the parameters.

Problem

This class will replace the boiler plate code to send emails in Apex.

Solution

Add this class to your Organizations Util class, or add it as a standalone class.

 public class EmailUtil {
        private Messaging.SingleEmailMessage singleEmailMessage;
        private final List<String> toAddresses;
        
        //optional parameters set to default        
        private String subject = '';
        private String htmlBody = ''; 
        private Boolean useSignature = false;
        private List<Messaging.EmailFileAttachment> fileAttachments = null;
        //defaults to current user's first name + last name
        private String senderDisplayName = UserInfo.getFirstName()+' '+UserInfo.getLastName();
        //get the current user in context
        User currentUser = [Select email from User where username = :UserInfo.getUserName() limit 1];        
        //replyTo defaults to current user's email 
        private String replyTo = currentUser.email;
        private String plainTextBody = '';
        
        public EmailUtil(List<String> addresses) {
            this.toAddresses = addresses;
        }
        
        public EmailUtil senderDisplayName(String val) {
            senderDisplayName = val;
            return this;
        }
        
        public EmailUtil subject(String val) {
            subject = val;
            return this;
        }
        
        public EmailUtil htmlBody(String val) {
            htmlBody = val;
            return this;
        }
        
        public EmailUtil useSignature(Boolean bool) {
            useSignature = bool;
            return this;
        }
        
        public EmailUtil replyTo(String val) {
            replyTo = val;
            return this;
        }
        
        public EmailUtil plainTextBody(String val) {
            plainTextBody = val;
            return this;
        }
        
        public EmailUtil fileAttachments(List<Messaging.Emailfileattachment> val) {
            fileAttachments = val;
            return this;
        }
        
        //where it all comes together
        //this method is private and is called from sendEmail()
        private EmailUtil build() {
            singleEmailMessage = new Messaging.SingleEmailMessage();
            singleEmailMessage.setToAddresses(this.toAddresses);
            singleEmailMessage.setSenderDisplayName(this.senderDisplayName);
            singleEmailMessage.setSubject(this.subject);
            singleEmailMessage.setHtmlBody(this.htmlBody);
            singleEmailMessage.setUseSignature(this.useSignature);
            singleEmailMessage.setReplyTo(this.replyTo);
            singleEmailMessage.setPlainTextBody(this.plainTextBody);
            singleEmailMessage.setFileAttachments(this.fileAttachments);
            return this;
        }
        
        //send the email message
        public void sendEmail() {
               try {
                   //call build first to create the email message object
                   build();
                   Messaging.sendEmail(new Messaging.SingleEmailMessage[] { singleEmailMessage });
               } catch (Exception ex) {
                   throw new GenericException('There was a problem while calling Messaging.sendEmail()');
               }                
        }    
            
    } 
 

The code is self-explanatory. The GenericException in the catch clause is optional, you could simply return if you don't want to throw an exception.

 //custom exception		
 public class GenericException extends Exception{
		
 }

Discussion

   List<String> toAddresses = new List<String> {'john.doe@acme.org'};
   String replyToAddress = 'john.duh@acme.org';
   //use the new util class to send an email
   EmailUtil emailUtil = new EmailUtil(toAddresses);
   //send plain text body
   emailUtil.plainTextBody('Bilbo Bagginses has stolen our Preciousssss!!')
				 .senderDisplayName('Gollum Gollum')
				 .replyTo(replyToAddress)
				 .sendEmail();
   //send html body
   emailUtil = new EmailUtil(toAddresses);
   emailUtil.htmlBody('I want my Ring back Frodo Baggins.')
				 .senderDisplayName('Saurons Eye')
				 .subject('One Ring to Rule them all')
				 .useSignature(true)
				 .replyTo(replyToAddress)
				 .sendEmail();