i can add the values with copy functionaliyt, but can any one help me in the remove all and remove selected functionality in salesforce with the below code .
v.f.page:

<apex:page controller="test11cntrl">
   <apex:form >
   
            <apex:selectList id="Avilblecities" multiselect="true" tabindex="1"  value="{!copyselectedvallist}" >  
                     <apex:selectOptions value="{!NotselectedOptions}"/>
                  </apex:selectList>
                  <br/>
             <apex:commandButton value="copyselected" action="{!copyselected}"  rerender="selrdnr"/> <br/>
                 
                 <apex:commandButton value="Removeslected" action="{!removeselected}"  rerender="selrdnr"/><br/>
                 <apex:commandButton value="Removeall" action="{!removeall}"  rerender="selrdnr"/><br/>
                  <apex:outputPanel id="selrdnr">
                  <apex:selectList id="Selectedcites" multiselect="true" tabindex="1"  value="{!copyselectedvallist2}" >  
                          <apex:selectOptions value="{!selectedOptions}"/>
                  </apex:selectList>
                  </apex:outputPanel>
   </apex:form>
</apex:page>

Apex class:

public class test11cntrl {

  public list<string> copyselectedvallist{get;set;}
  public list<selectoption>NotselectedOptions{get;set;}
  public list<string> copyselectedvallist2{get;set;}
  public set<selectoption>selectedOptions{get;set;}
  
  public test11cntrl(){
    copyselectedvallist= new list<string>();
    NotselectedOptions= new list<selectoption>();
    copyselectedvallist2= new list<string>();
    selectedOptions= new set<selectoption>();
     citylist = new list<string>();
     citydetails();
   }
   
   public list<string> citylist{get;set;}
   public void citydetails(){
        citylist.add('mumbai'); 
        citylist.add('maharastra');
        citylist.add('uttarpradesh');
       
       for(string s:citylist){
        NotselectedOptions.add(new SelectOption(s,s));
        }
   }
    
   public void copyselected(){
       for(string s: copyselectedvallist){
           Selectedoptions.add(new SelectOption(s,s));
         }
   }
    
    
    public void removeselected(){
    //remove the selected cites
    
    }
    
    public void removeall(){
     //remove all cities
    }
   
}

Can anyone ,help to handle the removeall frm seleced cities and remove only selectedcites functionality

thanks and regards
soumya sree