Change private static final field using Java reflection

Question

I have a class with a private static final field that, unfortunately, I need to change it at run-time.

Using reflection I get this error: java.lan

Answer 1

In case of presence of a Security Manager, one can make use of AccessController.doPrivileged

Taking the same example from accepted answer above:

import java.lang.reflect.*;

public class EverythingIsTrue {
    static void setFinalStatic(Field field, Object newValue) throws Exception {
        field.setAccessible(true);
        Field modifiersField = Field.class.getDeclaredField("modifiers");

        // wrapping setAccessible 
        AccessController.doPrivileged(new PrivilegedAction() {
            @Override
            public Object run() {
                modifiersField.setAccessible(true);
                return null;
            }
        });

        modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        field.set(null, newValue);
    }

    public static void main(String args[]) throws Exception {      
      setFinalStatic(Boolean.class.getField("FALSE"), true);
      System.out.format("Everything is %s", false); // "Everything is true"
    }
}

In lambda expression, AccessController.doPrivileged, can be simplified to:

AccessController.doPrivileged((PrivilegedAction) () -> {
    modifiersField.setAccessible(true);
    return null;
});