title: What's the method-type of JVM type signature
body: <p>According to the  <a href="https://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/types.html#wp16432" rel="nofollow noreferrer">JVM Specification</a>, 
  there are 11 type signatures of JVM, one of them is 'method type', i never see it. what is it ? </p>