How do I invoke a private static method using reflection (Java)?

Question

I would like to invoke a private static method. I have its name. I've heard it can be done using Java reflection mechanism. How can I do it?

EDIT: One problem I encountered when trying to invoke the method is how to specify the type of its argument. My method receives one argument and its type is Map. Therefore I cannot do Map<User, String>.TYPE (In run time there's no such a thing as Map because of Java Type erasure). Is there another way to get the method?

Answer 1

Let's say you want to call MyClass.myMethod(int x);

Method m = MyClass.class.getDeclaredMethod("myMethod", Integer.TYPE); m.setAccessible(true); //if security settings allow this Object o = m.invoke(null, 23); //use null if the method is static 

Answer 2

Invoke main from reflection tutorial

import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.Arrays;  public class InvokeMain {     public static void main(String... args) {     try {         Class<?> c = Class.forName(args[0]);         Class[] argTypes = new Class[] { String[].class };         Method main = c.getDeclaredMethod("main", argTypes);         String[] mainArgs = Arrays.copyOfRange(args, 1, args.length);         System.out.format("invoking %s.main()%n", c.getName());         main.invoke(null, (Object)mainArgs);          // production code should handle these exceptions more gracefully     } catch (ClassNotFoundException x) {         x.printStackTrace();     } catch (NoSuchMethodException x) {         x.printStackTrace();     } catch (IllegalAccessException x) {         x.printStackTrace();     } catch (InvocationTargetException x) {         x.printStackTrace();     }     } }