A.java

private static final ObjectMapper OM = new ObjectMapper();
private static final String STR = "hello world - the quick brown fox jumps over " 
        + "the lazy dog\r\n\r\nand here's " 
        + "a random slash\\, and some \"s";
        
@Benchmark
public void jsonStringSerialization(final Blackhole blackhole) throws Exception {
    byte[] obj = OM.writeValueAsBytes(STR);
    blackhole.consume(new String(obj, 1, obj.length - 2, StandardCharsets.UTF_8));
}

@Benchmark
public void jsonStringManual(final Blackhole blackhole) {
    String str = STR;
    if (str.contains("\\")) {
        str = str.replace("\\", "\\\\");
    }
    if (str.contains("\"")) {
        str = str.replace("\"", "\\\"");
    }
    blackhole.consume(str);
}