Fixing issue 486 @SubParameter Problems

src/main/java/com/beust/jcommander/ParameterDescription.java

@@ -300,7 +300,10 @@ private Object handleSubParameters(String value, int currentIndex, Class<?> type
           objectValue = type.newInstance();
           parameterized.set(object, objectValue);
         }
+        boolean access = sai.field.isAccessible();
+        sai.field.setAccessible(true); // before using the field, set accessible to true
         wrappedParameter.addValue(parameterized, objectValue, value, sai.field);
+        sai.field.setAccessible(access); // after using the field, set accessible to origin
         finalValue = objectValue;
       } catch (InstantiationException | IllegalAccessException e) {
         throw new ParameterException("Couldn't instantiate " + type, e);

src/main/java/com/beust/jcommander/WrappedParameter.java

@@ -81,6 +81,32 @@ public void addValue(Parameterized parameterized, Object object, Object value, F
           throws IllegalAccessException {
     if (parameter != null) {
       if (field != null) {
+        Class<?> fieldClass = field.getType();
+        if (fieldClass != value.getClass()) {
+          if (fieldClass == boolean.class || fieldClass == Boolean.class)
+            value = Boolean.parseBoolean(value.toString());
+          else if (fieldClass == byte.class || fieldClass == Byte.class)
+            value = Byte.parseByte(value.toString());
+          else if (fieldClass == short.class || fieldClass == Short.class)
+            value = Short.parseShort(value.toString());
+          else if (fieldClass == int.class || fieldClass == Integer.class)
+            value = Integer.parseInt(value.toString());
+          else if (fieldClass == long.class || fieldClass == Long.class)
+            value = Long.parseLong(value.toString());
+          else if (fieldClass == char.class || fieldClass == Character.class)
+            value = value.toString().charAt(0);
+          else if (fieldClass == float.class || fieldClass == Float.class)
+            value = Float.parseFloat(value.toString());
+          else if (fieldClass == double.class || fieldClass == Double.class)
+            value = Double.parseDouble(value.toString());
+          else {
+            try {
+              value = fieldClass.getConstructor(value.getClass()).newInstance(value);
+            } catch (InstantiationException | InvocationTargetException | NoSuchMethodException e) {
+              e.printStackTrace();
+            }
+          }
+        }
         field.set(object, value);
       } else {
         parameterized.set(object, value);