public void addInstanceField(EncodedField field) {
    if (field == null) {
      throw new NullPointerException("field == null");
    }

    instanceFields.add(field);
  }
Adds an instance field.

@param field {@code non-null;} the field to add
android/android_framework/dex-maker/src/main/java/com/android/dx/dex/file/ClassDataItem.java