Wat.java

// requires Java 19+

class WatSequence implements CharSequence {
    public CharSequence subSequence(int start, int end) {
        return this;
    }
    public int length() {
        return 2;
    }
    public char charAt(int index) {
        // look Ma, no concurrency!
        if (index == 1) throw new RuntimeException();
        return '⁉';
    }
    public String toString() {
        return "wat";
    }
}

class Wat {
    static String wat() {
        if (Runtime.version().feature() < 19) {
            throw new RuntimeException("this doesn't work pre java-19 :(");
        }

        StringBuilder sb = new StringBuilder();
        try {
            sb.append(new WatSequence());
        } catch (RuntimeException e) {}

        return new String(sb);
    }

    public static void main(String[] args) {
        String s = wat();
        System.out.println(s.isEmpty() && !s.equals(""));
    }
}