Order of execution in TestNG without using priority

I am using latest version of TestNG but still not able execute testcases by the order it has been written(avoiding priority annotation tag).

import org.testng.annotations.Test;
public class NewTest {
@Test
public void b() {
    System.out.println("inside b method");
}
@Test
public void a() {
System.out.println("inside a method");
}
}

I have also used IMethodInterceptor but still no go.

in testng.xml also added listeners:

<listeners>
<listener class-name="testngdemo.PriorityInterceptor" />
</listeners>

but still getting following output

inside a method
inside b method

IMethodInterceptor.png PriorityInterface.png