Java - Indent a string by curly braces

gistfile1.txt

public static String indent(String expression) {
    List<String> strings = Stream.of(expression)
        .map(e -> e.replace("{", "{#"))
        .map(e -> e.replace("}", "#}#"))
        .flatMap(e -> Arrays.stream(e.split("[#\\n]")))
        .map(String::trim)
        .filter(e -> !e.isEmpty())
        .collect(Collectors.toList());

    var indent = 0;
    StringBuilder sb = new StringBuilder();
    for (String string : strings) {
        if (string.equals("}")) {
            indent--;
        }
        sb.append("  ".repeat(indent)).append(string).append("\n");
        if (string.indexOf('{') != -1) {
            indent ++;
        }
    }

    return sb.toString();
}