初始化HashMap的一种特别方式

private static Map<String, ApplVerID> beginStringToApplVerID = new HashMap<String, ApplVerID>() {
        {
            // No support for earlier versions of FIX
            put(FixVersions.BEGINSTRING_FIX40, new ApplVerID(ApplVerID.FIX40));
            put(FixVersions.BEGINSTRING_FIX41, new ApplVerID(ApplVerID.FIX41));
            put(FixVersions.BEGINSTRING_FIX42, new ApplVerID(ApplVerID.FIX42));
            put(FixVersions.BEGINSTRING_FIX43, new ApplVerID(ApplVerID.FIX43));
            put(FixVersions.BEGINSTRING_FIX44, new ApplVerID(ApplVerID.FIX44));
            put(FixVersions.FIX50, new ApplVerID(ApplVerID.FIX50));
            put(FixVersions.FIX50SP1, new ApplVerID(ApplVerID.FIX50SP1));
            put(FixVersions.FIX50SP2, new ApplVerID(ApplVerID.FIX50SP2));
        }
    };