Getting nosuchmethod exception

Question

i am new to programming and here is my code

package first_project;
import java.lang.reflect.*; 
import java.util.Scanner;

public class My_Class {

    public static void main(String[] args)throws Exception {
        Scanner sc=new Scanner(System.in);
        //Getting numbers from user
        System.out.println("Enter First Number:");
        int a=sc.nextInt();
        System.out.println("Enter Second Number:");
        int b=sc.nextInt();
        //code for private method
        Class c=addition.class;  
        Method m = addition.class.getDeclaredMethod("add(a,b)");
        m.setAccessible(true);  
        m.invoke(c);
    }
}

package first_project;

//Class for addition
public class addition{
    private void add(int a,int b)
    {
        int ans= a+ b;
        System.out.println("addition:"+ans);
    }
}

This is exception:

Exception in thread "main" java.lang.NoSuchMethodException: first_project.addition.add(int a,int b)() at java.base/java.lang.Class.getDeclaredMethod(Class.java:2434) at first_project.My_Class.main(My_Class.java:15)

score 3 · Answer 1 · 2018-12-13T18:08:17.360

The Method.getDeclaredMethod accepts as arguments the method name and the parameter types. You have to change it like this Method m = addition.class.getDeclaredMethod("add", int.class, int.class);

The method invocation is also wrong:

m.invoke(c);

should be:

m.invoke(*instance of addition*, *first param*, *second param*);

Replace *instance of addition* etc. accordingly.

Also, Java uses some code conventions like: the class name must start with a capital letter etc.

Aditya Narayan Dixit · Accepted Answer · 2018-12-13T18:03:21.533

2

Change this line :

addition.class.getDeclaredMethod("add(a,b)");

to this:

Method method = addition.class.getDeclaredMethod("add", int.class, int.class);

getDeclaredMethod takes method name and its parameters type as argument.

To invoke the method:

method.invoke(new addition(), a, b);

edited Dec 13 '18 at 18:03

answered Dec 13 '18 at 17:54

Aditya Narayan Dixit

1,845
8
18

Furthermore, when calling `m.invoke` you should pass 3 arguments: the first one is an instance of the class `addition` while the 2nd and 3rd parameters should be your `a` and `b` – Robert Kock Dec 13 '18 at 17:59
Thanks, missed writing that. Updated the answer. – Aditya Narayan Dixit Dec 13 '18 at 18:01
The first parameter should be an `instance` of the class, not the class itself. So use `m.invoke(c.newInstance(), a, b);` – Robert Kock Dec 13 '18 at 18:02
the small "a" in additional got me thinking it was an instance. Thanks for pointing out. – Aditya Narayan Dixit Dec 13 '18 at 18:04
still getting same exception after changing line.Can you please check code in your free time – Vaibhav Chavan Dec 13 '18 at 18:06
did you change this line: `m.invoke(c)` to this: `method.invoke(new addition(), a, b);` – Aditya Narayan Dixit Dec 13 '18 at 18:08

Getting nosuchmethod exception

2 Answers2