@Override
    public String toString() {
        StringBuilder ret = new StringBuilder();
        ret.append("switch { ");
        for (Map.Entry<String, Expression> entry : cases.entrySet()) {
            ret.append("case \"").append(StringUtilities.escape(entry.getKey(), '"')).append("\": ");
            Expression exp = entry.getValue();
            ret.append(exp).append("; ");
        }
        if (defaultExp != null) {
            ret.append("default: ").append(defaultExp).append("; ");
        }
        ret.append("}");
        return ret.toString();
    }
The default expression, or null if none
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/SwitchExpression.java