Using SonarLint Plugin 5.1.0.34721 for IntelliJ gives a hint based on S1612 for line with mapToObj:
Replace this lambda with method reference ‘char.class::cast’.
    public static void main(String[] args) {
        final List<Character> characters = "abc"
                .chars()
                .mapToObj(i -> (char) i)
                .collect(Collectors.toList());
        
        characters.forEach(c->System.out.println("char: "+c));
    }
After changing the code it produces a ClassCastException at runtime:
Cannot cast java.lang.Integer to char
