Cannot Instantiate class error when running Dummy TestsB

Cannot Instantiate class error when running Dummy TestsB , I am trying to generate initial extent report .
I am getting the following error....
Please see the attached screen shot , I am not sure where I am going wrong , I am just following the video !
KINDLY HELP ! SOS !

Cannot instantiate class com.selenium.core.ddf.testcases.DummyTestC
at org.testng.internal.ObjectFactoryImpl.newInstance(ObjectFactoryImpl.java:40)
at org.testng.internal.ClassHelper.createInstance1(ClassHelper.java:382)
at org.testng.internal.ClassHelper.createInstance(ClassHelper.java:295)
at org.testng.internal.ClassImpl.getDefaultInstance(ClassImpl.java:118)
at org.testng.internal.ClassImpl.getInstances(ClassImpl.java:183)
at org.testng.internal.TestNGClassFinder.<init>(TestNGClassFinder.java:128)
at org.testng.TestRunner.initMethods(TestRunner.java:416)
at org.testng.TestRunner.init(TestRunner.java:242)
at org.testng.TestRunner.init(TestRunner.java:212)
at org.testng.TestRunner.<init>(TestRunner.java:166)
..
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