Hi SPR,

Here is teh solution: it might have syntax errors as i ddint execute it .Please modify it accordingly:

<apex:page controller="sendEmail">
 <apex:form >
Group name : <apex:inputText value="{!publicgroupname}" />// select group here
 <apex:commandButton value="SendEmails" action="{!sendingEmail}"/> <br/>
  Email Status :<b> {!message}  </b>
 </apex:form>
</apex:page>


public class sendEmail{    


    public List<string> getPublicGroups {get;set;}
    public string toAddress{get;set;}
    public string message{get;set;}
    
    public List<String> getEmailAddresses() {
    List<String> mailToAddresses = new List<String>();
    List<User> users = [SELECT Email FROM User WHERE Id IN (
                            SELECT UserOrGroupId
                            FROM GroupMember
                            WHERE Group.Name = :'Group Name'
                        )];

    for(User u : users)
        mailToAddresses.add(u.email);

    return mailToAddresses;
}
    
    public sendEmail(){
    
    
     //get lis of public groups here and display as drop down in vf page
    
    
    }
    
    public PageReference sendingEmail(){                
        Messaging.SingleEmailMessage semail = new Messaging.SingleEmailMessage();
        String[] toWhom = new String[]{getEmailAddresses()};
        semail.setToAddresses(toWhom);
        semail.setSubject('Single Email message Example');
        semail.setPlainTextBody('Hello!!!!!This is a test email to test single email message program');
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] {semail});
        message='Email Sent !!!';
        return null;
    }
}