This question was asked originally here: https://stackoverflow.com/questions/72787286/executable-hasrealparameterdata-and-parameter-isnamepresent-dont-work-as-ex but as soon as I got no answer I've decided to try it here adding some concerns regarding JavaDoc of Parameter.isNamePresent()
With ad-hoc built JDK 19 (having exposed `Executable.hasRealParameterData()`) I take the code public class Main { public static void main(String[] args) throws NoSuchMethodException { Method foo = Main.class.getMethod("foo", String.class, int.class); System.out.println(foo.hasRealParameterData()); } public void foo(String parameter1, int parameter2) {} } and compile it with % javac Main.java Then I run compiled Java class and it prints `false` into console. This is fine because decompiled `Main` class looks like public class Main { //... public void foo(String var1, int var2) {} // parameter names are not 'real' } i.e. parameter names are synthetic. This behaviour is understandable. Then I take the same Java sources and recompile the class with javac -g:vars Main.java I run the same code again and again it prints `false` to console. This puzzles me, because now the compiled code looks different: public class Main { //... public void foo(String parameter1, int parameter2) {} // parameter names are 'real' } Same happens if for recompilation I use plain -g flag (generates all auxiliary data). Now let's stop calling JDK's private API and rely only on the methods available out-of-the-box, e.g. `Parameter.isNamePresent()` (this one calls `Executable.hasRealParameterData()` under the hood): public static void main(String[] args) throws NoSuchMethodException { Method foo = Main.class.getMethod("foo", String.class, int.class); Parameter parameter1 = foo.getParameters()[0]; Parameter parameter2 = foo.getParameters()[1]; System.out.println(parameter1.isNamePresent()); System.out.println(parameter2.isNamePresent()); } public void foo(String parameter1, int parameter2) {} And again, no matter how I compile the sources, this code prints `false false`. So my two questions are 1) whether this is a bug or am I doing something wrong? 2) is it possible somehow to change the behaviour to have at least Parameter.isNamePresent() returning true P.S. Parameter.isNamePresent() works unexpectedly even when I run it on conventional, not hacked JDK. P.P.S. In compiled code I see 'real' parameter names, but if I stop at debug point in IDEA parameter name is suddenly `arg0` in `Parameter.name` field. P.P.P.S. I think that JavaDoc of Parameter.isNamePresent() should be changed as soon as now it points out to 'MethodParameters' attribute of a class file which is confusing to me as to end user of Java because I cannot understand from plain Java code what are those 'MethodParameters' and what will be returned for any of my methods.