package io.growingabit.app.model;

import org.apache.commons.lang3.StringUtils;
import org.joda.time.DateTime;

import com.google.common.base.Preconditions;

import io.growingabit.app.utils.SecureStringGenerator;

public class StudentConfirmationPhone {

  private static final int VERIFICATION_CODE_LENGTH = 8;

  private String phoneNumber;
  private transient String verificationCode;
  private transient Long tsExpiration;
  transient String originHost;

  public StudentConfirmationPhone(final String phoneNumber, final String originHost) {
    Preconditions.checkArgument(StringUtils.isNotEmpty(phoneNumber));
    Preconditions.checkArgument(StringUtils.isNotEmpty(originHost));
    this.originHost = originHost;
    this.phoneNumber = phoneNumber;
    this.verificationCode = generateVerificationCode();
    this.tsExpiration = new DateTime().plusDays(7).getMillis();
  }

  @SuppressWarnings("unused")
  private StudentConfirmationPhone() {
    // only used by Objectify to instantiate the object
  }

  public String getPhoneNumber() {
    return this.phoneNumber;
  }

  public String getVerificationCode() {
    return this.verificationCode;
  }

  public Long getTsExpiration() {
    return this.tsExpiration;
  }

  public String getOriginHost() {
    return this.originHost;
  }

  private String generateVerificationCode() {
    return new SecureStringGenerator(VERIFICATION_CODE_LENGTH).nextNumericString();
  }

}

@@ -776,16 +776,21 @@
 nCode = 
+this.
 generate

Organize all imports