import com.liferay.portal.kernel.util.StringPool;
import com.liferay.portal.model.User;
import com.liferay.portal.service.ServiceContext;
import com.liferay.portal.service.UserLocalServiceUtil;
import com.liferay.portal.util.PortalInstances;

int startUserId = 100;
int maxUserCount = 400;

User user = null;
ServiceContext serviceContext = new ServiceContext();

long creatorUserId = 0;
long companyId = PortalInstances.getDefaultCompanyId();

boolean autoPassword = false;
String password1 = "perf";
String password2 = "perf";
boolean autoScreenName = false;
String screenName = "perf";
String emailAddress = "perf@liferay.com";
long facebookId = 0;
String openId = com.liferay.portal.kernel.util.StringPool.BLANK;
Locale locale = Locale.US;
String firstName = "PERF";
String middleName = com.liferay.portal.kernel.util.StringPool.BLANK;
String lastName = "USER";
int prefixId = 0;
int suffixId = 0;
boolean male = true;
int birthdayMonth = Calendar.JANUARY;
int birthdayDay = 1;
int birthdayYear = 1970;
String jobTitle = StringPool.BLANK;
long[] groupIds = null;
long[] organizationIds = null;
long[] roleIds = null;
long[] userGroupIds = null;
boolean sendEmail = false;

for (int ui = startUserId; ui < startUserId + maxUserCount; ++ui) {
  screenName = "perf"+ui;
  try { user = UserLocalServiceUtil.getUserByScreenName(companyId, screenName); } catch (Exception e) {user = null;}
  if (user == null) {
    emailAddress = screenName + "@liferay.com";
    try {
      user = UserLocalServiceUtil.addUser(
      creatorUserId, companyId, autoPassword, password1, password2,
      autoScreenName, screenName, emailAddress, facebookId, openId,
      locale, firstName, middleName, lastName, prefixId, suffixId, male,
      birthdayMonth, birthdayDay, birthdayYear, jobTitle, groupIds,
      organizationIds, roleIds, userGroupIds, sendEmail, serviceContext);
    } catch(Exception e) {}
  }
}