private static double invoke(@Nullable MethodHandle mh) {
        if (mh == null) {
            return Double.NaN;
        }

        try {
            return (double) mh.invoke(operatingSystemBean);
        } catch (Throwable e) {
            return Double.NaN;
        }
    }
Instantiates a new Default cpu health checker.

@param targetSystemCpuUsage the target cpu usage
@param targetProcessCpuUsage the target process cpu usage
core/src/main/java/com/linecorp/armeria/server/healthcheck/CpuHealthChecker.java