Add a Geocode to a Custom Address Field

1public class GeoCodeExample {
2    @future(callout=true)
3    public static void parseJSONResponse() {  
4        double lat;
5        double lng;
6        String city = null;
7        String street = null;
8           String stateCode = null; 
9        String countryCode = null;
10        
11        Account record = [SELECT Mailing_Address__c FROM Account WHERE Id = 'Account ID'];
12        Address customAddress = record.Mailing_Address__c;
13        
14        //Remove white spaces from address components
15        if(customAddress.getCity() != null){
16             city = customAddress.getCity().deleteWhitespace();
17        }
18        if(customAddress.getStreet() != null){
19             street = customAddress.getStreet().deleteWhitespace();
20        }
21        if(customAddress.getStateCode() != null){
22             stateCode = customAddress.getStateCode();
23        }
24        if(customAddress.getCountryCode() != null){
25             countryCode = customAddress.getCountryCode();
26        }    
27        
28        //concatenate strings
29        String address = street+city+stateCode+countryCode;
30        
31        String key='API key';
32        Http httpProtocol = new Http();
33        // Create HTTP request to send.
34        HttpRequest request = new HttpRequest();
35        // Set the endpoint URL.
36        // USING GOOGLE MAP API 
37        String endpoint = 'https://maps.googleapis.com/maps/api/geocode/json?address='+address+'&key='+key;
38        request.setEndPoint(endpoint);
39        // Set the HTTP verb to GET.
40        request.setMethod('GET');
41        // Send the HTTP request and get the response.
42        // The response is in JSON format.
43        HttpResponse response = httpProtocol.send(request);
44      
45       // Parse JSON response to get all the totalPrice field values.
46        JSONParser parser = JSON.createParser(response.getBody());
47        
48        while (parser.nextToken() != null) {
49            if ((parser.getCurrentToken() == JSONToken.FIELD_NAME) && 
50                (parser.getText() == 'lat')) {
51                parser.nextToken();
52                // Get latitude
53                lat = parser.getDoubleValue();
54           
55                parser.nextToken();
56                parser.nextToken();
57                //Get longitude    
58                lng = parser.getDoubleValue();
59                 } 
60              }
61        // Update lat long of account record
62        record.Mailing_Address__Latitude__s=lat;
63        record.Mailing_Address__Longitude__s=lng;
64        update record;
65    }
66}

1<apex:page id="pg" controller="GeoCodeExample">
2<apex:form >
3    <apex:pageBlock id="pb">
4        <apex:pageBlockButtons >
5            <apex:commandButton value="Get GeoCode For Custom Address Field" 
6            action="{!parseJSONResponse}"/>
7        </apex:pageBlockButtons>
8    </apex:pageBlock>
9</apex:form>
10</apex:page>