How can remove JSON parsing Error

i write the below code to get data from WebAPI but it through the following errors how can remove this...
and one more thing that which IP address use for URL in genymotion Emulator
>> Caused by: java.lang.NullPointerException
>> at com.example.finalproject.Login$Myclass.doInBackground(Login.java:88)

package com.example.finalproject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
//import java.net.URI;
import java.net.URL;
//import java.net.URLConnection;
import java.nio.charset.MalformedInputException;
//import java.security.PublicKey;

//import android.R.string;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
//import android.util.Log;
//import android.view.Menu;
//import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Login extends Activity {
	
	TextView tvget;
	Button btnget;
	@Override
	
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_login);
		
		btnget=(Button)findViewById(R.id.btnjson);
		tvget=(TextView)findViewById(R.id.tvjson);
		
		btnget.setOnClickListener(new View.OnClickListener() {@Override
		public void onClick(View v) {
		//	Log.i("Error", "It's working");
			new Myclass().execute("http://192.168.1.201/newAPI/api/user");
		}
			
			
		});
		
	}		
		

	public class Myclass extends AsyncTask<String, String, String>{
	
		
		
		@Override
		protected String doInBackground(String... params) {
			HttpURLConnection connection= null;
			BufferedReader reader = null ;
			
			try {
			URL url=new URL(params[0]);
	connection=(HttpURLConnection)url.openConnection();
	connection.connect();
	InputStream instrm=connection.getInputStream();
	reader=new BufferedReader(new InputStreamReader(instrm));
	StringBuffer b=new StringBuffer() ;
	//String line="";
	while (reader.readLine()!=null) 
	{//line=reader;
		b.append(reader);

	}
	
	return b.toString();
	
	
		} 
			catch (MalformedInputException e) {
			e.printStackTrace();
		}
		
			catch (IOException e) {
		e.printStackTrace();	
		
		}
		finally {
			connection.disconnect();
			try {
				reader.close();
			} catch (IOException e2) {
				
			e2.printStackTrace();
			}
		}
		return null;
		
		
	}	//doinbackground method body end
				
		@Override
		protected void onPostExecute(String result) {
			
			super.onPostExecute(result);
					
			tvget.setText(result);
		}
	}//jsontask class body end
	
	}