Accessing methods with primitive argument via reflection

[kumarjit banerjee]

Can a method be invoked via reflection api of java which contains a primitive in the argument.

For example I want to access the method "show" from another class via reflection.


public class Example1{

public void show(int i,String s){
System.out.println("Value is "+i+" "+s);
}

}

[Matthew Brown]

Yes, it can. Which part are you having trouble with? Getting the Method object or calling invoke on it?

If it's the first part - note that you can get Class objects representing primitives from the appropriate wrapper class. For example, Integer.TYPE is "The Class instance representing the primitive type int" according to the Javadocs.

For the second part, the Javadocs for invoke say: "Individual parameters are automatically unwrapped to match primitive formal parameters".

So something like this should work:

Method method = Example.class.getMethod("show", Integer.TYPE, String.class);
method.invoke(ex, 20, "With reflection");

[kumarjit banerjee]

Matthew Brown wrote:Yes, it can. Which part are you having trouble with? Getting the Method object or calling invoke on it?

If it's the first part - note that you can get Class objects representing primitives from the appropriate wrapper class. For example, Integer.TYPE is "The Class instance representing the primitive type int" according to the Javadocs.

For the second part, the Javadocs for invoke say: "Individual parameters are automatically unwrapped to match primitive formal parameters".

So something like this should work:

Method method = Example.class.getMethod("show", Integer.TYPE, String.class);
method.invoke(ex, 20, "With reflection");

Thanks very much. It worked.

[Darryl Burke]

you can get Class objects representing primitives from the appropriate wrapper class. For example, Integer.TYPE ...

Isn't Integer.TYPE the same as int.class?

[Matthew Brown]

If such a thing exists, almost certainly .

[Campbell Ritchie]

Matthew Brown wrote:If such a thing exists, almost certainly .

Can't be. Try this

public class IntClassDemo
{
    private Class<?> intClass = int.class;
    
    public static void main(String[] args)
    {
        new IntClassDemo().printDifference();
    }
    
    public void printDifference()
    {
        System.out.printf("intClass == Integer.TYPE? %b%n", intClass == Integer.TYPE);
    }
}

java IntClassDemo
intClass == Integer.TYPE? true

[Matthew Brown]

Campbell Ritchie wrote:

Matthew Brown wrote:If such a thing exists, almost certainly .

Can't be. Try this

Hang on. It's late on a Friday night, and I really shouldn't be trying to follow code at this point...but doesn't that prove that they are the same, which is what I just said?

[Campbell Ritchie]

Matthew Brown wrote:. . . but doesn't that prove that they are the same, which is what I just said?

Damn! He noticed!

Yes, of course they are the same.