void (final int spaces, final int indent) { if (spaces < 0 || indent < 0) { throw new IllegalStateException("Neither spaces: " + spaces + " or indent " + indent + " should be null"); } performModification(() -> { if (!isKeepFirstColumn() || getFlag(CONTAINS_SPACES_INITIALLY_MASK)) { mySpaces = spaces; myIndentSpaces = indent; } }); }