method newProxyInstance in class java.lang.reflect.Proxy cannot be applied to given types

Question about the task

Resolved

This line:

return (SomeInterfaceWithMethods)Proxy.newProxyInstance(new CustomInvocationHandler(original));

gives the following error:

Error in com/codegym/task/task32/task3205/Solution.java on line 28
method newProxyInstance in class java.lang.reflect.Proxy cannot be applied to given types;
  required: java.lang.ClassLoader,java.lang.Class<?>[],java.lang.reflect.InvocationHandler
  found: com.codegym.task.task32.task3205.CustomInvocationHandler
  reason: actual and formal argument lists differ in length

1) In a separate file, create a public CustomInvocationHandler class that will be the invocation handler when creating a proxy object.
2) CustomInvocationHandler must support the InvocationHandler interface.
3) CustomInvocationHandler must have one public constructor with a single SomeInterfaceWithMethods parameter.
4) Before calling any of the original object's methods, the phrase "<methodName> in" must be displayed.
5) After calling one of the original object's methods, the phrase "<methodName> out" must be displayed.
6) Implement the getProxy() method, which must create a proxy (Proxy.newProxyInstance(...)).
See the example output in the main() method.
The main() method is not tested.

Requirements:

There must be a CustomInvocationHandler class.
The CustomInvocationHandler class must support the InvocationHandler interface.
The CustomInvocationHandler class must have one public constructor with a single SomeInterfaceWithMethods parameter.
Before calling any of the original object's methods, the phrase "<methodName> in" must be displayed.
After calling one of the original object's methods, the phrase "<methodName> out" must be displayed.
The getProxy() method must create a proxy for the SomeInterfaceWithMethods interface.

package com.codegym.task.task32.task3205; import java.lang.reflect.Proxy; /* Creating a proxy object */ public class Solution { public static void main(String[] args) { SomeInterfaceWithMethods obj = getProxy(); obj.stringMethodWithoutArgs(); obj.voidMethodWithIntArg(1); /* Expected output: stringMethodWithoutArgs in inside stringMethodWithoutArgs stringMethodWithoutArgs out voidMethodWithIntArg in inside voidMethodWithIntArg inside voidMethodWithoutArgs voidMethodWithIntArg out */ } public static SomeInterfaceWithMethods getProxy() { SomeInterfaceWithMethods original = new SomeInterfaceWithMethodsImpl(); return (SomeInterfaceWithMethods)Proxy.newProxyInstance(new CustomInvocationHandler(original)); } }

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Han

Level 24 , Netherlands

4 November 2019, 16:14

Then the explanation in the article before this task seems weird it says:

Reader reader = (Reader)Proxy.newProxyInstance(new CustomInvocationHandler());
reader.close();

Roman

Level 41

30 October 2019, 13:48

solution

Method newProxyInstance takes the following parameters: ClassLoader loader, Class[] interfaces, InvocationHandler h but you try to put CustomInvocationHandler there...