selenium web driver java.lang.NoClassDefFoundError: com/google/gson/JsonSyntaxException

trying to run simple test selenium Web Driver program which is mentioned below:

package com.abc;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;

public class Mock_Exam {

    /**
     * @param args   
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        WebDriver driver = new FirefoxDriver();
        driver.get("https://www.google.co.in/");

    }

}

after running as java application getting the below error :

Exception in thread "main" java.lang.NoClassDefFoundError: com/google/gson/JsonSyntaxException
    at org.openqa.selenium.firefox.Preferences.readDefaultPreferences(Preferences.java:95)
    at org.openqa.selenium.firefox.Preferences.<init>(Preferences.java:65)
    at org.openqa.selenium.firefox.FirefoxProfile.<init>(FirefoxProfile.java:87)
    at org.openqa.selenium.firefox.FirefoxProfile.<init>(FirefoxProfile.java:77)
    at org.openqa.selenium.firefox.FirefoxProfile.<init>(FirefoxProfile.java:66)
    at org.openqa.selenium.firefox.FirefoxDriver.getProfile(FirefoxDriver.java:262)
    at org.openqa.selenium.firefox.FirefoxDriver.startClient(FirefoxDriver.java:239)
    at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:114)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:193)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:186)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:182)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:95)
    at com.kesdee.ia.Mock_Exam.main(Mock_Exam.java:14)
Caused by: java.lang.ClassNotFoundException: com.google.gson.JsonSyntaxException
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 13 more

FireFox version: 36.0.1 Selenium: selenium-java-2.45.0