Method concat

java/lib/src/main/java/io/github/ccxt/Helpers.java:811–832

(Object a, Object b)

    }

    public static Object concat(Object a, Object b) {
        if (a == null && b == null) return null;
        if (a == null) return b;
        if (b == null) return a;

        if (a instanceof List && b instanceof List) {
            List result = new ArrayList((List) a);
            result.addAll((List) b);
            return result;
        } else if (a instanceof List && !(b instanceof List)) {
            List result = new ArrayList((List) a);
            result.add(b);
            return result;
        } else if (!(a instanceof List) && b instanceof List) {
            List result = new ArrayList();
            result.add(a);
            result.addAll((List) b);
            return result;
        } else {
            throw new IllegalStateException("Unsupported types for concatenation.");
        }
    }

    // --------- helpers ---------