//We can also store our username password in custom setting.
    String username='xxx';//salesforce username
    String password='xxxx';//EUe4eHjMxXb8UFco1SPcpsZL9';//salesforce password+securitytoken
    // Generating the Access Token
    HttpRequest req = new HttpRequest();
    req.setMethod('POST');
    req.setEndpoint('https://login.salesforce.com/services/oauth2/token');// this is the OAuth endpoint where this request will be hit
    req.setBody('grant_type=password&client_id='+clientId+'&client_secret='+clientSecret+'&username='+username+'&password='+password);

    Http http = new Http();
    HTTPResponse res = http.send(req);
    String str = res.getBody();
    wrapObj = (Wrapper)Json.deserialize(str,Wrapper.class);
    accessToken = wrapObj.access_token;
    instanceUrl = wrapObj.instance_url;
    methodGet();
}

// Retrieve the Contacts from the otehr org.
public void methodGet(){
    HttpRequest req = new HttpRequest();
    req.setMethod('GET');
    //req.setEndpoint(wrapObj.instance_url+'/services/apexrest/Account/getAccountById?name=champaKAli');

    req.setEndpoint('https://lightningwebsite-dev-ed.my.salesforce.com/services/apexrest/AccountService');
    req.setHeader('Authorization', 'Bearer'+wrapObj.access_token);
    Http http = new Http();
    HTTPResponse res = http.send(req);

    System.debug('***Response***** ' + res.getBody());
    //---------------------Here ------------------
    /*JSONParser parser = JSON.createParser(res.getBody());
    do{
        parser.nextToken();
    }while(parser.hasCurrentToken() && !'records'.equals(parser.getCurrentName()));
        parser.nextToken();
    List<account> acc = (List<Account>) parser.readValueAs(List<Account>.class);*/
}
public Contact con {get;set;}
public String s1 {get;set;}
public String accessToken;
public String instanceUrl;
public Wrapper wrapObj{get;set;}
// Wrapper Class to Store the value from the Jason.
public class Wrapper{
    String id;
    String instance_url;
    String access_token;
    String issued_at;
    String signature;
}