iam getting an error while addding the data to the Selectlist using the Repeat functionality ..!

public class test5 {

  public list<string> lststatename{get;set;}
  public list<string> lstrating{get;set;}
  
  public list<string> lstactive{get;set;}
  public map<string, string> statemap{get;set;}

 
 public test5(){
 
 
    string  jsonexample1 =  ' { "overalldata": [ {"stateName": "Andrapradesh",  "rating": "5.0" , "active": "yes" }, { "stateName": "Telangana",  "rating": "4.0" ,"active": "no" }, {"stateName": "Banglore",  "rating": "5.0" ,"active": "no"} , {"stateName": "Maharastra",  "rating": "4.5" ,"active": "no" }  ] } ';

   
     map<string,object>  metadatamap= (map<string,object>)json.deserializeuntyped(jsonexample1); 
     
      list<object>  values1= (list<object>)metadatamap.get('overalldata');
        
        
         lststatename= new list<string>();
         lstrating= new list<string>();
         statemap= new map<String, string>();
         
          for(object parsed : values1){
          map<string,object>  values = (map<string,object>)parsed;
          string statename = string.valueof(values.get('stateName'));
          
          string rating= string.valueof(values.get('rating'));
          
          lststatename.add(statename);
             
          lstrating.add(rating);
             
             statemap.put(statename,rating);
             
             }
            
 }
}

Visualforce page:
 

<apex:page controller="test5" >

 <apex:form >
   <apex:repeat value="{!statemap}" var="a">
    <apex:selectList  value="{!selectedvalue}">   
               <apex:selectOptions value="{!a}">{!a}</apex:selectOptions>
<apex:actionsupport event="onchange" />
         </apex:selectList>
   
   </apex:repeat>
            
    The selected value is:{!selectedvalue} and rating is:                                       
      
 
 </apex:form>
 
</apex:page>

//to add the label as the statename and its value as the rating.. onchange should ahave to display ..!