java.lang.NumberFormatException: For input string: ""    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)    at java.lang.Long.parseLong(Long.java:601)    at java.lang.Long.parseLong(Long.java:631)    at java.text.DigitList.getLong(DigitList.java:195)    at java.text.DecimalFormat.parse(DecimalFormat.java:2051)    at java.text.SimpleDateFormat.subParse(SimpleDateFormat.java:1867)    at java.text.SimpleDateFormat.parse(SimpleDateFormat.java:1514)    at java.text.DateFormat.parse(DateFormat.java:364)    at com.sz.core.utils.DateUtils.toDate(DateUtils.java:50)

起因是SimpleDateFormat 线程不安全

http://www.cnblogs.com/peida/archive/2013/05/31/3070790.html