Call a method with String[] parameter using reflection

Question

I have used all the suggestions I could find on StackOverflow and other sites for this. I am trying to invoke a method using reflection. Here is the code for my method:

public void my_method(String[] args) {

    for(int i=0; i<args.length; i++)
    {
        System.out.println(args);
    }
}

Here is the code I used for reflection

Class[] paramStringArray = new Class[1];    
paramStringArray[0] = String[].class;
String[] argu = {"hey", "there"};

Method method = cls.getDeclaredMethod("my_method", paramStringArray);
method.invoke(obj, new Object[]{argu});

My issue is that when I run the program, I see the output printed as: [Ljava.lang.String;@70a6aa31 [Ljava.lang.String;@70a6aa31

I have tried all the suggestions I could find. Can someone please help me with this?

Thanks!

Object#toString() is your keyword. Why are you trying the advanced topic of reflection when you don't yet know how to print an object? Slow down. — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Jul 24, 2013 at 20:04
args is a String[]. It does not have a custom toString() method to print its contents. Use Arrays.toString(args); to return a String with the contents of the array. — Sotirios Delimanolis
– Sotirios Delimanolis, Commented Jul 24, 2013 at 20:18

Óscar López · Accepted Answer · 2013-07-24 20:10:41Z

1

The method my_method() receives as a parameter a String[], not a String. You're calling a different method. The code should look like this:

paramString[0] = String[].class;
Method method = cls.getDeclaredMethod("my_method", paramString);

To invoke it, pass a String[] as parameter:

method.invoke(obj, new String[]{"x"});

Also, the body of the loop in my_method() should refer to each element's position, not to the array itself:

System.out.println(args[i]);

edited Jul 24, 2013 at 20:10

answered Jul 24, 2013 at 20:05

Óscar López

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5 Comments

Sotirios Delimanolis Over a year ago

Maybe paramStringArray is String[].class.

Óscar López Over a year ago

I'm betting the code was not copied correctly, so it's hard to know what's the real problem

user2033666 Over a year ago

Well, I tried Object#toString() before posting this question. Thanks, for the suggestion though

user2033666 Over a year ago

Sorry, my bad in typing the code. I actually have it the way you mentioned. I will edit the question.

Óscar López Over a year ago

@user2033666 ok, if that was not the problem then look at the last part in the answer - you're printing the array and not the contents of the array, use this to fix it: System.out.println(args[i]);

Lee Meador · Accepted Answer · 2013-07-24 20:09:59Z

1

You need to print args[i] and not what you have.

Also the method should be called with a new String[] instead of new Object[].

answered Jul 24, 2013 at 20:09

Lee Meador

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1 Comment

user2033666 Over a year ago

Oh!! that was a really silly typo I made.. I changed it to args[i] and it works great now. :) Thanks so much for noticing that!

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