Buen día, tengo una duda con un metodo para implementar paypal nativa para android, tengo el siguiente metodo:

public void initLibrary() {
PayPal pp = PayPal.getInstance();
if (pp == null) {
pp = PayPal.initWithAppID(this, Util.sand_box.id, PayPal.ENV_SANDBOX);
}
}

Pero en la linea: pp = PayPal.initWithAppID(this, Util.sand_box.id, PayPal.ENV_SANDBOX);
me marca un error el "Util.sand_box.id" en particular la palabra "Util" me la pone en rojo, y me manda un mensaje que dice: Cannot resolve symbol 'Util'

Ah que se debe ese error? tengo todas mis librerias hasta la de import java.util.*;

Espero me puedan ayudar, saludos

Hola disculpen la tardanza, esta es la clase con todo el código y sus imports, espero me puedan ayudar, saludos...

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.paypal.android.MEP.PayPal;
import com.paypal.android.MEP.PayPalActivity;
import com.paypal.android.MEP.PayPalAdvancedPayment;
import com.paypal.android.MEP.PayPalPayment;
import com.paypal.android.MEP.PayPalReceiverDetails;

import java.math.BigDecimal;

public class MainActivity extends ActionBarActivity {

public final int PAYPAL_RESPONSE = 100;
EditText editText_friend1_id;
EditText editText_friend1_amount;
EditText editText_friend2_id;
EditText editText_friend2_amount;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editText_friend1_id = (EditText) findViewById(R.id.editText_friend1_id);
editText_friend1_amount = (EditText) findViewById(R.id.editText_friend1_amount);
editText_friend2_id = (EditText) findViewById(R.id.editText_friend2_id);
editText_friend2_amount = (EditText) findViewById(R.id.editText_friend2_amount);
Button paypal_button = (Button) findViewById(R.id.button_paypal_mpl);

initLibrary();
paypal_button.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {
PayPalButtonClick(editText_friend1_id.getText().toString(),
editText_friend1_amount.getText().toString(),
editText_friend2_id.getText().toString(),
editText_friend2_amount.getText().toString());
}
});
}

public void initLibrary() {
PayPal pp = PayPal.getInstance();
if (pp == null) {
pp = PayPal.initWithAppID(this, Util.sand_box.id, PayPal.ENV_SANDBOX);
}
}

public void PayPalButtonClick(String primary_id, String primary_amount,
String secoundary_id, String secoundary_amount) {

//Codigo para pago basico en paypal
//PayPalPayment newPayment = new PayPalPayment();
//newPayment.setSubtotal(new BigDecimal("1.0"));
//newPayment.setCurrencyType("MXN");
//newPayment.setRecipient("Email-de-notificacion@hotmail.com");
//newPayment.setMerchantName("Mi compañia");
//Log.d("Pavan", "Llamando intencion");
//if(PayPal.getInstance() != null){
// Log.d("Pavan", "In if");
//Intent paypalIntent = PayPal.getInstance().checkout(newPayment, this);
//startActivityForResult(paypalIntent, 1);

Log.d("pavan", "primary " + primary_id);
Log.d("pavan", "primary_amount " + primary_amount);

Log.d("pavan", "secoundry_amount " + secoundary_amount);
Log.d("pavan", "secoundry_id " + secoundary_id);

//config reciever1
PayPalReceiverDetails receiver0, receiver1;
receiver0 = new PayPalReceiverDetails();
receiver0 .setRecipient(primary_id);
receiver0.setSubtotal(new BigDecimal(primary_amount));

//config reciever2
receiver1 = new PayPalReceiverDetails();
receiver1.setRecipient(secoundary_id);
receiver1.setSubtotal(new BigDecimal(secoundary_amount));

//Agregando tipo de pago
PayPalAdvancedPayment advPayment = new PayPalAdvancedPayment();
advPayment.setCurrencyType("MXN");

advPayment.getReceivers().add(receiver0);
advPayment.getReceivers().add(receiver1);

Intent papalIntent = PayPal.getInstance().checkout(advPayment, this);
this.startActivityForResult(papalIntent, PAYPAL_RESPONSE);
}

public void onActivityResult(int requestCode, int resultCode, Intent data){
Log.d("pavan", "response");

if(requestCode == PAYPAL_RESPONSE){

switch (resultCode){
case Activity.RESULT_OK:
//El pago fue exitoso
String paykey = data.getStringExtra(PayPalActivity.EXTRA_PAY_KEY);
Log.d("pavan", "success" + paykey);
Toast.makeText(getApplicationContext(), "Pago realizado con exito",
Toast.LENGTH_LONG).show();
break;
case Activity.RESULT_CANCELED:
Toast.makeText(getApplicationContext(), "Pago cancelado, intente de nuevo",
Toast.LENGTH_LONG).show();
break;

case PayPalActivity.RESULT_FAILURE:
Toast.makeText(getApplicationContext(), "Fallo el pago, intente de nuevo",
Toast.LENGTH_LONG).show();
break;

}
}

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();

//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}

return super.onOptionsItemSelected(item);
}
}

PD: O si ya tienen un ejemplo corriendo de paypal que me puedan facilitar se los agradeceria mucho, estoy programando en android studio 1.5