java-native-access/jna · error · IllegalArgumentException

Can't create an instance of <klass>, requires a public no-ar

Error message

Can't create an instance of <klass>, requires a public no-arg constructor: <cause>

What it means

Klass.newInstance wraps reflection failures (IllegalAccess, NoSuchMethod, InstantiationException, etc.) into this IllegalArgumentException when it cannot instantiate the class via its public no-arg constructor. JNA uses it internally to create instances of Structure, Callback and similar types.

Source

Thrown at src/com/sun/jna/Klass.java:52

    /**
     * Create a new instance for the given {@code klass}. Runtime exceptions
     * thrown from the constructor are rethrown, all other exceptions
     * generated from the reflective call are wrapped into a
     * {@link java.lang.IllegalArgumentException} and rethrown.
     *
     * @param klass desired class to instantiate
     * @return the new instance
     * @throws IllegalArgumentException if the instantiation fails
     * @throws RuntimeException if the constructor for {@code klass} throws
     *         a runtime exception
     */
    public static <T> T newInstance(Class<T> klass) {
        try {
            return klass.getDeclaredConstructor().newInstance();
        } catch (IllegalAccessException | IllegalArgumentException | InstantiationException | NoSuchMethodException | SecurityException e) {
            String msg = "Can't create an instance of " + klass
                    + ", requires a public no-arg constructor: " + e;
            throw new IllegalArgumentException(msg, e);
        } catch (InvocationTargetException e) {
            if (e.getCause() instanceof RuntimeException) {
                throw (RuntimeException) e.getCause();
            } else {
                String msg = "Can't create an instance of " + klass
                        + ", requires a public no-arg constructor: " + e;
                throw new IllegalArgumentException(msg, e);
            }
        }
    }
}

View on GitHub (pinned to d036ad9781)

Solutions

1. Add a public no-arg constructor to the class (make it static if nested).
2. Use the overload that accepts a preallocated instance, e.g. Structure's use of newInstance with a target object.
3. If the class is abstract or an interface, instantiate a concrete subclass instead.
4. Check the wrapped cause `e` in the message for the exact reflection failure.

Example fix

// before
class Point { Point(int x, int y) {} }
// after
class Point { public Point() {} public Point(int x, int y) {} }

static boolean hasPublicNoArgCtor(Class<?> k) {
  try { k.getDeclaredConstructor(); return java.lang.reflect.Modifier.isPublic(k.getModifiers()) && !java.lang.reflect.Modifier.isAbstract(k.getModifiers()); }
  catch (NoSuchMethodException e) { return false; }
}

static <T> T safeNewInstance(Class<T> k) {
  if (!hasPublicNoArgCtor(k)) throw new IllegalArgumentException(k + " lacks a public no-arg ctor");
  return com.sun.jna.Klass.newInstance(k);
}

try {
  T t = Klass.newInstance(klass);
} catch (IllegalArgumentException e) {
  if (e.getMessage().contains("requires a public no-arg constructor")) {
    throw new IllegalStateException("Make " + klass.getSimpleName() + " static/concrete with a public no-arg ctor", e.getCause());
  }
  throw e;
}

When it happens

Trigger: Calling Klass.newInstance(klass) on a class with no declared no-arg constructor, a non-public no-arg constructor, an abstract class, or an interface; a SecurityException from the SecurityManager.

Common situations: Nested (non-static inner) classes whose implicit constructor needs an enclosing instance; classes with only parameterized constructors; anonymous/local classes; instantiating interfaces by mistake.

Related errors

• Can't instantiate " + type
• Instantiation of " + type + " (Pointer) not allowed, is it p
• Exception thrown while instantiating an instance of " + type
• No suitable constructor found for class:
• Failed to call addSuppressedMethod

AI-assisted analysis of java-native-access/jna@d036ad9781 (2026-09-12). Data as JSON: /api/errors/9146f818b5df5d4c. Report an issue: GitHub.