CODEWITHSUNDEEP
javaarraysreflection
Tom
Tom

Reputation: 6971

IllegalArgumentException with constructing class using reflection and array arguments

running the following code:

public class Test {

    public Test(Object[] test){

    }

    public static void main(String[] args) throws Exception{
            Constructor cd = Test.class.getConstructor(Object[].class);
            Object[] objs = {1, 2, 3, 4, 5, 6, 7, 8};
            cd.newInstance(objs);
    }
}

I get the error :

Exception in thread "main" java.lang.IllegalArgumentException: wrong number of arguments
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:532)
    at groupd.poker.utils.tests.ai.nqueens.Test.main(Test.java:17)

Why is this?

Upvotes: 9

Views: 6830

Answers (1)

Craig Suchanec
Craig Suchanec

Reputation: 10824

The newInstance() method of the constructor class takes an array of objects. Each item in the array is an argument of the constructor you are invoking. Your class's constructor takes an object array so you need to have an object array inside the array you pass to the new instance method

public static void main(String[] args) throws Exception{
            Constructor cd = Test.class.getConstructor(Object[].class);
            Object[] objs = {1, 2, 3, 4, 5, 6, 7, 8};
            Object[] passed = {objs};
            cd.newInstance(passed);
    }

Upvotes: 12

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