注意一个object是否相等的问题

String s = “a”；

boolean b1 = (s=="a");
boolean b2 = s.equals("a");

b1 and b2 will both be true. (in java)

String s = new String(“a”)；

boolean b1 = (s=="a");
boolean b2 = s.equals("a");

b1 will be false, while b2 is still true.

Be aware!