Extent Report issue

hello ,

Please help me in generating extent reports. when i am trying to generate extent report getting below error

"Cannot instantiate class com.qtpselenium.core.ddf.testcases.Extent_Reports"

i am using Extent_reports class and ExtentManager

package com.qtpselenium.core.ddf.testcases;

import org.openqa.selenium.WebDriver;
import org.testng.Assert;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.AfterSuite;
import org.testng.annotations.BeforeSuite;
import org.testng.annotations.Test;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.BeforeTest;

import com.qtpselenium.core.ddf.base.BaseTest;
import com.qtpselenium.core.ddf.util.ExtentManager;
import com.relevantcodes.extentreports.ExtentReports;
import com.relevantcodes.extentreports.ExtentTest;
import com.relevantcodes.extentreports.LogStatus;

public class Extent_Reports extends BaseTest {

ExtentReports rep = ExtentManager.getInstance();
ExtentTest test;
WebDriver driver;

@BeforeSuite // once before executing all tests in all java files
public void initliazSelenium(){
//Selenium object - Webdriver
System.out.println("in the begining - initilize selenium");
test = rep.startTest("dummy test reports");
test.log(LogStatus.INFO, "Starting the test");
openBrowser("Moxilla");
test.log(LogStatus.INFO, "Generate reports ....");
navigate("appurl");
test.log(LogStatus.PASS, "test passed");

}

@AfterSuite
public void ShutdownSelenium(){
//shutdown Selenium object - Webdriver
System.out.println("in the end - close selenium");

}

@BeforeTest // Before executing all test cases
public void ConnecttoDB() {
System.out.println("Connecting to DB");
}


@BeforeMethod
public void OpenBrowser() {
System.out.println("OpenBrowser");
}

@AfterMethod
public void quit() {
System.out.println("Closereports");
rep.endTest(test);
rep.flush();

}


}