如果str为null
str = null;
str.equals("")报空指针,nullPointerException
写为“”.equals(str)可以避免空指针,nullPointerException
October 17, 2017 9:27 PM
2017.10.7
如果str为null
str = null;
str.equals("")报空指针,nullPointerException
写为“”.equals(str)可以避免空指针,nullPointerException
October 17, 2017 9:27 PM
2017.10.7