How to Get Method Parameter Names and Types Using Java Reflection?

Obtaining Method Parameter Names via Java Reflection

Problem:

Given a Java class with a method that accepts parameters, how can you determine the parameter's name and type using Java reflection?

Solution:

In Java 8 and later, the Parameter class provides access to parameter names. To obtain parameter information:

import java.lang.reflect.Method;
import java.lang.reflect.Parameter;

public class ParameterNames {

    public static void getParameterNames(Method method) {
        Parameter[] parameters = method.getParameters();

        for (Parameter parameter : parameters) {
            System.out.printf("Parameter name: %s, Type: %s%n", parameter.getName(), parameter.getType().getName());
        }
    }

    public static void main(String[] args) {
        try {
            Method method = Whatever.class.getMethod("aMethod", int.class);
            getParameterNames(method);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }
    }

    public static class Whatever {
        public void aMethod(int aParam) {
        }
    }
}

Output:

Parameter name: aParam, Type: int

Important Note:

For this to work, you need to specify the -parameters argument when compiling your Java code. For example, for Maven users:

<configuration>
    <parameters>true</parameters>
    <compilerArgument>-parameters</compilerArgument>
</configuration>

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