Integer源码的getInteger(String nm, Integer val)方法的第一个参数描述是the system property with the specified name.那么实际上到底nm是什么？

    public static Integer getInteger(String nm, Integer val) {
        String v = null;
        try {
            v = System.getProperty(nm);
        } catch (IllegalArgumentException | NullPointerException e) {
        }
        if (v != null) {
            try {
                return Integer.decode(v);
            } catch (NumberFormatException e) {
            }
        }
        return val;