Java Reflection cannot call getMethod with primitive type [duplicate]

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• Java Reflection calling constructor with primitive types 5 answers

I have few class like this.

interface AsyncCallback {
    void onComplete(Object response);
}

class Impl {
    public String bar(String i, String j) {
        return i + j;
    }
}

class Async {

    private final Impl impl;

    public Async() {
        impl = new Impl();
    }

    public void bar(String i, String j, AsyncCallback callback) {
        callAsync("bar", callback, new Object[]{i, j});
    }

    private Class[] getParamsClasses(Object[] params) {
        ArrayList<Class> classes = new ArrayList<>();
        for (Object param : params) {
            classes.add(param.getClass());
        }
        return classes.toArray(new Class[classes.size()]);
    }


    private void callAsync(String methodName, AsyncCallback callback, Object[] params) {
        try {
            Thread.sleep(1000);
            Class[] paramClasses = getParamsClasses(params);
            Method methodToCall = impl.getClass().getMethod(methodName, paramClasses);
            Object response;
            response = methodToCall.invoke(impl, params);
            callback.onComplete(response);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

And then I put them together into this

    Async a = new Async();
    a.bar("1", "2", new AsyncCallback() {

        @Override
        public void onComplete(Object response) {
            System.out.println(response);
        }
    });

This works, outputting string "12" to stdout.

But when I tried adding new method using primitive type.

class Impl {
    //new method
    public int foo(int i, int j, int k) {
        return i + j + k;
    }
}

class Async {
    //new method
    public void foo(int i, int j, int k, AsyncCallback callback) {
        callAsync("foo", callback, new Object[]{i, j, k});
    }
}

And I tried using the new method.

    a.foo(1, 2, 3, new AsyncCallback() {

        @Override
        public void onComplete(Object response) {
            System.out.println(response);
        }
    });

It should return the string "3" to stdout. But instead it threw Exception

java.lang.NoSuchMethodException: Impl.foo(java.lang.Integer, java.lang.Integer, java.lang.Integer)

Why this happens and how to fix this?