8242208: Use Method.getParameterCount where applicable

Reviewed-by: redestad, chegar

src/java.base/share/classes/java/lang/invoke/MethodHandleProxies.java

@@ -276,13 +276,13 @@ private static boolean isObjectMethod(Method m) {
         switch (m.getName()) {
         case "toString":
             return (m.getReturnType() == String.class
-                    && m.getParameterTypes().length == 0);
+                    && m.getParameterCount() == 0);
         case "hashCode":
             return (m.getReturnType() == int.class
-                    && m.getParameterTypes().length == 0);
+                    && m.getParameterCount() == 0);
         case "equals":
             return (m.getReturnType() == boolean.class
-                    && m.getParameterTypes().length == 1
+                    && m.getParameterCount() == 1
                     && m.getParameterTypes()[0] == Object.class);
         }
         return false;

src/java.base/share/classes/java/lang/reflect/Executable.java

@@ -378,7 +378,7 @@ public int getParameterCount() {
     private void verifyParameters(final Parameter[] parameters) {
         final int mask = Modifier.FINAL | Modifier.SYNTHETIC | Modifier.MANDATED;
 
-        if (getParameterTypes().length != parameters.length)
+        if (getParameterCount() != parameters.length)
             throw new MalformedParametersException("Wrong number of parameters in MethodParameters attribute");
 
         for (Parameter parameter : parameters) {

src/java.base/share/classes/sun/reflect/annotation/AnnotationType.java

@@ -121,7 +121,7 @@ private AnnotationType(final Class<? extends Annotation> annotationClass) {
             if (Modifier.isPublic(method.getModifiers()) &&
                 Modifier.isAbstract(method.getModifiers()) &&
                 !method.isSynthetic()) {
-                if (method.getParameterTypes().length != 0) {
+                if (method.getParameterCount() != 0) {
                     throw new IllegalArgumentException(method + " has params");
                 }
                 String name = method.getName();