8273656: Improve java.lang.invoke.MethodType.parameterList() and its usage

Reviewed-by: jvernee, vlivanov, mchung

Author: stsypanov

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

@@ -5882,8 +5882,8 @@ private static void filterReturnValueChecks(MethodType targetType, MethodType fi
         BoundMethodHandle result = target.rebind();
         LambdaForm lform = result.editor().collectReturnValueForm(filterType.basicType());
         MethodType newType = targetType.changeReturnType(filterType.returnType());
-        if (filterType.parameterList().size() > 1) {
-            for (int i = 0 ; i < filterType.parameterList().size() - 1 ; i++) {
+        if (filterType.parameterCount() > 1) {
+            for (int i = 0 ; i < filterType.parameterCount() - 1 ; i++) {
                 newType = newType.appendParameterTypes(filterType.parameterType(i));
             }
         }
@@ -6735,7 +6735,7 @@ private static List<Class<?>> longestParameterList(Stream<MethodHandle> mhs, int
                         filter(t -> t.parameterCount() > skipSize).
                         map(MethodType::parameterList).
                         reduce((p, q) -> p.size() >= q.size() ? p : q).orElse(empty);
-        return longest.size() == 0 ? empty : longest.subList(skipSize, longest.size());
+        return longest.isEmpty() ? empty : longest.subList(skipSize, longest.size());
     }
 
     private static List<Class<?>> longestParameterList(List<List<Class<?>>> lists) {
@@ -7019,7 +7019,7 @@ private static void whileLoopChecks(MethodHandle init, MethodHandle pred, Method
         List<Class<?>> outerList = innerList;
         if (returnType == void.class) {
             // OK
-        } else if (innerList.size() == 0 || innerList.get(0) != returnType) {
+        } else if (innerList.isEmpty() || innerList.get(0) != returnType) {
             // leading V argument missing => error
             MethodType expected = bodyType.insertParameterTypes(0, returnType);
             throw misMatchedTypes("body function", bodyType, expected);
@@ -7349,7 +7349,7 @@ private static void countedLoopChecks(MethodHandle start, MethodHandle end, Meth
         List<Class<?>> innerList = bodyType.parameterList();
         // strip leading V value if present
         int vsize = (returnType == void.class ? 0 : 1);
-        if (vsize != 0 && (innerList.size() == 0 || innerList.get(0) != returnType)) {
+        if (vsize != 0 && (innerList.isEmpty() || innerList.get(0) != returnType)) {
             // argument list has no "V" => error
             MethodType expected = bodyType.insertParameterTypes(0, returnType);
             throw misMatchedTypes("body function", bodyType, expected);
@@ -7573,7 +7573,7 @@ private static Class<?> iteratedLoopChecks(MethodHandle iterator, MethodHandle i
         List<Class<?>> internalParamList = bodyType.parameterList();
         // strip leading V value if present
         int vsize = (returnType == void.class ? 0 : 1);
-        if (vsize != 0 && (internalParamList.size() == 0 || internalParamList.get(0) != returnType)) {
+        if (vsize != 0 && (internalParamList.isEmpty() || internalParamList.get(0) != returnType)) {
             // argument list has no "V" => error
             MethodType expected = bodyType.insertParameterTypes(0, returnType);
             throw misMatchedTypes("body function", bodyType, expected);

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

@@ -792,7 +792,7 @@ public Class<?> returnType() {
      * @return the parameter types (as an immutable list)
      */
     public List<Class<?>> parameterList() {
-        return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
+        return List.of(ptypes);
     }
 
     /**