CODEWITHSUNDEEP
javareflection
Laurent Cosserat
Laurent Cosserat

Reputation: 1

Invoking by reflection a private static method

When I call java.lang.reflect.Method.invoke() method on a private static method, I get a "java.lang.IllegalArgumentException : wrong number of arguments". I think I respect javadoc specification, did I something wrong ? Thanks for any help.

Here is my code :

public class MyClass {
    ....
    private static Object myMethod(String[] stringArray) {...}
}

I want to test myMethod() in a JUnit test class :

public class MyClassTest {
    private static String[] myArray = {"A", "B", "C"};
    @Test
    public void myMethodTest() {
        Method method = Class.forName("mypackage.MyClass").getDeclaredMethod("myMethod", myArray.getClass());
        method.setAccessible(true);
        method.invoke(null, myArray);
    }
}

Upvotes: 0

Views: 426

Answers (2)

Robby Cornelissen
Robby Cornelissen

Reputation: 97341

You need to wrap your String in an object array:

Method method = Class.forName("mypackage.MyClass")
        .getDeclaredMethod("myMethod", myArray.getClass());
method.setAccessible(true);
method.invoke(null, new Object[] {myArray});

The second parameter to method.invoke() requires an array or vararg of the method's arguments. For your method, you only have a single argument (which also happens to be an array), but you still need to wrap it in an array.

Upvotes: 0

JB Nizet
JB Nizet

Reputation: 692181

Since invoke() takes a vararg as argument, the Java compiler considers each element of the array that you pass as a vararg argument, i.e. it considers it equivalent to

method.invoke(null, "A", "B", "C");

You can just cast your array to an object to fix the issue:

method.invoke(null, (Object) myArray);

Upvotes: 2

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