strange error in java reflection (processing)

问题

From an answer in this my previous question: how to create in best way an instance from the class object

I'm trying to do what he suggests but I don't know how to fix the error.

Code:

import java.lang.reflect.*;

class Foo {
   public <T> T create(float x, float y, Class<T> myClass) 
   throws Exception {
      Constructor<T> toCall = myClass.getConstructor(float.class, float.class);
      return toCall.newInstance(x, y);
  }
}

class Dog {
   public Dog(float x, float y) {
      print(x);
      print(y);
   } 
}

Foo foo = new Foo();

try {
   foo.create(10.0f, 10.0f, Dog.class);
 } catch (Exception e) {
   print(e);
}

Exception:

java.lang.NoSuchMethodException: sketch_140319d$1Dog.<init>(float, float)

回答1:

As I have just commented on your other question, this won't work if Dog is a non-static inner class of sketch_140319, which the error message suggests. I guess you stripped out the sketch_140319 class from your question - I don't know why you did that, when this is what the problem was.

You need to either make Dog static, or add sketch_140319.class as the first argument to getConstructor and an instance of sketch_140319 as the first argument to newInstance.

回答2:

you can't call

foo.create(10.0, 10.0, Dog.class);

because 10.0 is a double, not a float

to call it like a float, do

foo.create(10.0f, 10.0f, Dog.class);

Update: my code is

class Dog {
    public Dog(float x, float y) {
        print(x);
        print(y);
    }

    private void print(float x) {
        System.out.println(x);
    }
}

and

import java.lang.reflect.Constructor;

class Foo {
   public <T> T create(float x, float y, Class<T> myClass) 
   throws Exception {
      Constructor<T> toCall = myClass.getConstructor(float.class, float.class);
      return toCall.newInstance(x, y);
  }
}

and

public class SomeOtherClass {

    /**
     * @param args
     */
    public static void main(String[] args) {
        Foo foo = new Foo();

        try {
           foo.create(10.0f, 10.0f, Dog.class);
         } catch (Exception e) {
           e.printStackTrace();
        }

    }
}

and it returned

10.0
10.0

来源：https://stackoverflow.com/questions/22495012/strange-error-in-java-reflection-processing

标签

java

class

reflection

processing