System.QueryException: List has more than 1 row for assignment to SObject at method fine

Question

When im running the below soql its work fine

SELECT BillingCountry,BillingCity, Industry, (SELECT Id, Name,Amount , StageName FROM Opportunities) FROM Account  WHERE BillingCountry = 'USA'

its work fine but when i customized this query into

SELECT BillingCountry,BillingCity, Industry, (SELECT Id, Name,Amount , StageName FROM Opportunities) FROM Account

salesforce returing this error.

Here is the method where i run this query

public PageReference find() 
    {         
        String id = UserInfo.getUserId();
        User activeUser = [Select Email From User where id = :id limit 1];
        String email = activeUser.Email;

        HttpRequest req = new HttpRequest();
        HttpResponse res = new HttpResponse();
        Http http = new Http();

        req.setEndpoint('http://52.37.182.4/public/checkUser/'+email);
        req.setMethod('GET');
        req.setCompressed(false);
        req.setBody('key1=value1&key2=value2');
        req.setHeader('Content-Type', 'application/json'); 

        try {
            res = http.send(req);
        } catch(System.CalloutException e) {
            System.debug('Callout error: '+ e);
        }

        Boolean userExsist = (Boolean)JSON.deserialize(res.getBody(), Boolean.class);

        if(!userExsist)
        {
            showPopup();
            return null;
        }                            

        lstResultWrapper = new List<ResultWrapper>();
        for(Account c : [SELECT BillingCountry,BillingCity, Industry, (SELECT Id, Name,Amount , StageName FROM Opportunities) FROM Account WHERE BillingCountry='USA'])
        {
                req.setEndpoint('http://52.37.182.4/public/checkDeal/'+c.Opportunities[0].Name);
                req.setMethod('GET');
                req.setCompressed(false);
                req.setBody('key1=value1&key2=value2');
                req.setHeader('Content-Type', 'application/json'); 

                try {
                    res = http.send(req);
                } catch(System.CalloutException e) {
                    System.debug('Callout error: '+ e);
                    return null;
                }

                Boolean dealExsist = (Boolean)JSON.deserialize(res.getBody(), Boolean.class);

// error indicating on the below line       
                ResultWrapper result = new ResultWrapper(c,c.Opportunities, !dealExsist);
                lstResultWrapper.add(result);                                    

        }

        return null;
    }     

Edited :

Visual Force page

<apex:pageBlock id="tableId2">
                 <apex:outputText value="{!result}"></apex:outputText> 
                <apex:pageBlockTable value="{!lstResultWrapper}" var="items" id="table">

                    <apex:column headerValue="Deal Title"> 
                    <apex:outputText value="{!items['opportunity'].Name}"/> 
                    </apex:column> 

                    <apex:column headerValue="Deal Value"> 
                    <apex:outputText value="{!items['opportunity'].Amount}"/> 
                    </apex:column> 

                    <apex:column headerValue="Stage"> 
                    <apex:outputText value="{!items['opportunity'].StageName}"/> 
                    </apex:column> 

                    <apex:column headerValue="Industry"> 
                    <apex:outputText value="{!items['account'].Industry}"/> 
                    </apex:column> 

                    <apex:column headerValue="Country"> 
                    <apex:outputText value="{!items['account'].BillingCountry}"/> 
                    </apex:column> 

                    <apex:column headerValue="City"> 
                    <apex:outputText value="{!items['account'].BillingCity}"/> 
                    </apex:column> 


                    <apex:column headerValue="Action"> 
                        <apex:commandButton value="Find Clozer" onclick="displayResult" action="{!createDeal}" rendered="{!IF(items['isCreated'], false, true)}" rerender="tableId2,table" >
                            <apex:param name="title" value="{!items['opportunity'].Name}" assignTo="{!title}" />
                             <apex:param name="dealValue" value="{!items['opportunity'].Amount}" assignTo="{!dealValue}" />
                             <apex:param name="stageName" value="{!items['opportunity'].StageName}" assignTo="{!stageName}" />
                             <apex:param name="ind" value="{!items['account'].Industry}" assignTo="{!ind}" />
                             <apex:param name="count" value="{!items['account'].BillingCountry}" assignTo="{!count}" />
                             <apex:param name="cty" value="{!items['account'].BillingCity}" assignTo="{!cty}" /> 
                        </apex:commandButton>
                    </apex:column>
                </apex:pageBlockTable>        

Answer 1

You need to update your ResultWrapper which currently accepting single opportunity but you are passing c.Opportunities which is list of opportunity so modify your ResultWrapper to accept list.

ResultWrapper result = new ResultWrapper(c,c.Opportunities, !dealExsist);

Wrapper class

public class ResultWrapper{
  public Account account {get;set;} 
  public List<Opportunity> opportunity {get;set;} 
  public Boolean isCreated {get;set;}

  public ResultWrapper(Account acc,List<Opportunity> opt,Boolean alreadyCreated) { 
         this.account = acc; 
         this.opportunity = opt; 
         this.isCreated = alreadyCreated; 
 } 
}

I don't know what is your logic behind this wrapper class but if you want to user single opportunity there is no need to modify wrapper class only pass single opportunity as shown below

ResultWrapper result = new ResultWrapper(c,c.Opportunities[0], !dealExsist);