Parameter name is always returned as "arg0"

Question

I'm using 'Parameter' class in java 8 to get the name of the parameter.

public class ParamTest {

public void newMethodParamTest() {
    try {
        Method[] declaredMethods = ParamTest.class.getDeclaredMethods();
        for (Method declaredMethod : declaredMethods) {
            if (declaredMethod.getName().equals("testObj")) {
                System.out.println(getParameterNames(declaredMethod));
                break;
            }
        }
    }
    catch(Exception e) {
        e.printStackTrace();
    }
}

public void testObj(int num) {
    System.out.println(num);
}

public static List<String> getParameterNames(Method method) {
    System.out.println(method.getName());
    Parameter[] parameters = method.getParameters();
    List<String> parameterNames = new ArrayList<>();

    for (Parameter parameter : parameters) {
        String parameterName = parameter.getName();
        parameterNames.add(parameterName);
    }
    return parameterNames;
}

public static void main(String[] args) {
    ParamTest test = new ParamTest();
    test.newMethodParamTest();
}

Now when I run this code the returned value is always arg0. What I was expecting to see is num.

in the code you've provided, you declared `public class ParamTest`, but then instantiated an object of type `Test1`. what is `Test1`? — Woodrow Barlow, Jul 01 '15 at 19:24
@user1629109 your code still references `Test1` and the code is still missing, so... the typo is not fixed. — Turing85, Jul 01 '15 at 19:33
you need `javac -parameter` - see http://stackoverflow.com/questions/21455403/how-to-get-method-parameter-names-in-java-8-using-reflection — ZhongYu, Jul 01 '15 at 19:36
@bayou.io: `javac -parameters` instead of `javac -parameter` — habsq, Jul 01 '15 at 20:00

Parameter name is always returned as "arg0"

0 Answers0