Need clarity on reflection API

I have this code in a .java file:
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import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Api_reflection {

public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
// TODO Auto-generated method stub
String x="saymehi";
Method method=Api_reflection.class.getMethod(x,String.class);
method.invoke(method,"saymehi");

}

public static void saymehi() {
// TODO Auto-generated method stub
System.out.println("hiiiiiiiiiiiiiiiiiiiiiiii");

}

}

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Am struck in understanding this-->

Method method=Api_reflection.class.getMethod(x,String.class);
method.invoke(method,"saymehi");

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Have understood that "Method" is a class & "method" reference,"Api_reflection" is the class in which 2 lines of code is present.

Am not able to understand, class.getMethod(x,String.class);

Can you explain this section in more detail please.

Regards,
Chaitra