Mock private static final field using mockito or Jmockit

One way is using reflection get rid of final modifier from the field and then replace the LOGGER field with Mocked one

public class Class1Test {
    @Test
    public void test() throws Exception {
        Logger logger = Mockito.mock(Logger.class);
        Mockito.when(logger.isInfoEnabled()).thenReturn(false);
        setFinalStatic(Class1.class.getDeclaredField("LOGGER"), logger);
        Class1 cls1 = new Class1();
        assertFalse(cls1.demoMethod());
    }

    static void setFinalStatic(Field field, Object newValue) throws Exception {
        field.setAccessible(true);        
        Field modifiersField = Field.class.getDeclaredField("modifiers");
        modifiersField.setAccessible(true);
        modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
        field.set(null, newValue);
    }
}