我如何知道在内部（成员）类上使用哪个构造函数？

Question

Reflective instantiation of an inner class requires a constructor that takes a synthetic parameter, the instance of the enclosing class. If the inner class is static, then there is no such constructor.

I can tell that a class is an inner class using the Class.isMemberClass() method, but I can't see a neat way of determining whether or not the member class is static or not, which is how I would expect to figure out which constructor to call.

Is there a neat way to tell?

Answer 1

See the Examining Class Modifiers tutorial. I think it's something like

Modifier.isStatic(myClass.getModifiers());

Answer 2

David is correct. I'm just going to post what you mean by

Reflective instantiation of an inner class requires a constructor that takes a synthetic parameter, the instance of the enclosing class.

for people like myself that needed to try it out:

public class Outer {
    public String value = "outer";

    public static void main(String[] args) throws Exception {
        int modifiers = StaticNested.class.getModifiers();
        System.out.println("StaticNested is static: " + Modifier.isStatic(modifiers));

        modifiers = Inner.class.getModifiers();
        System.out.println("Inner is static: " + Modifier.isStatic(modifiers));

        Constructor constructor = Inner.class.getConstructors()[0]; // get the only one
        Inner inner = (Inner) constructor.newInstance(new Outer()); // the constructor doesn't actually take arguments
    }

    public static class StaticNested {

    }

    public class Inner {
        public Inner() {
            System.out.println(Outer.this.value);
        }
    }
}

prints

StaticNested is static: true
Inner is static: false
outer