Question

I have a program where I need to find all instances of a class within an array. I would like to create a method that does this for me. For instance, if I have the array

Object[] arr = {"mystring", new Boolean(false), new Integer(4), new Character('i')}

and I called this method with argument of String (I’m not sure what the type of my argument should be, actually), it would return an array of {"mystring"}.

I’ve tried things like

public void printInstancesOf(Class c, Object[] array)
{
    for (Object obj : array)
    {
        if (obj instanceof c)
        {
             System.out.println(obj);
        }
    }
}

But that doesn’t even compile. Does anyone know how to do this? Or is it not possible to do?

Answer 1

Looks like you want Class.isInstance(Object o):

Determines if the specified Object is assignment-compatible with the object represented by this Class. This method is the dynamic equivalent of the Java language instanceof operator. The method returns true if the specified Object argument is non-null and can be cast to the reference type represented by this Class object without raising a ClassCastException. It returns false otherwise.

if (c.isInstance(obj) {
    System.out.println(obj);
}