IllegalAccessException on using reflection

Question

I was trying to learn reflection and I came across this IllegalAccessException. Please see the following code:

public class ReflectionTest
{
      public sta         


        

Answer 1

I suspect you should use getDeclaredMethod (among other issues). I don't bother to remember Reflection API details (they're for the compiler!), but in your case compare your code with that produced by dp4j:

$ javac -Averbose=true -All -cp dp4j-1.2-SNAPSHOT-jar-with-dependencies.jar ReflectionTest.java 
ReflectionTest.java:6: Note: 
import java.util.*;

public class ReflectionTest {

public ReflectionTest() {
    super();
}

@com.dp4j.Reflect()
public static void main(String[] args) throws java.lang.ClassNotFoundException, java.lang.NoSuchFieldException, java.lang.IllegalAccessException, java.lang.NoSuchMethodException, java.lang.reflect.InvocationTargetException, java.lang.InstantiationException, java.lang.IllegalArgumentException {
    final java.lang.reflect.Constructor hashSetConstructor = Class.forName("java.util.HashSet").getDeclaredConstructor();
    hashSetConstructor.setAccessible(true);
    Set myStr = (.java.util.Set<.java.lang.String>)hashSetConstructor.newInstance();
    final java.lang.reflect.Method addWithEMethod = Class.forName("java.util.Set").getDeclaredMethod("add", .java.lang.Object.class);
    addWithEMethod.setAccessible(true);
    addWithEMethod.invoke(myStr, new .java.lang.Object[1][]{"obj1"});
    final java.lang.reflect.Method iteratorMethod = Class.forName("java.util.Set").getDeclaredMethod("iterator");
    iteratorMethod.setAccessible(true);
    Iterator itr = (.java.util.Iterator)iteratorMethod.invoke(myStr);
    final java.lang.reflect.Method hasNextMethod = Class.forName("java.util.Iterator").getDeclaredMethod("hasNext");
    hasNextMethod.setAccessible(true);
    final java.lang.reflect.Method printlnWithbooleanMethod = Class.forName("java.io.PrintStream").getDeclaredMethod("println", .java.lang.Boolean.TYPE);
    printlnWithbooleanMethod.setAccessible(true);
    printlnWithbooleanMethod.invoke(System.out, new .java.lang.Object[1][]{hasNextMethod.invoke(itr)});
}

}

    public static void main(String[] args)
                       ^
...

$ java ReflectionTest
true

The only change you need to do is annotate your main method with @com.dp4j.Reflect:

$ vim ReflectionTest.java
import java.util.*;

public class ReflectionTest
{
        @com.dp4j.Reflect
        public static void main(String[] args)
        {
                Set myStr = new HashSet();
                myStr.add("obj1");
                Iterator itr = myStr.iterator();
                // Method mtd = itr.getClass().getMethod("hasNext");
                System.out.println(itr.hasNext());
        }
}

NB: this works only with dp4j-1.2-SNAPSHOT (I've just added suport for it). If you don't use Maven, download the jar from here. You find the test case with your problem here.