如果你只是用双引号换单，这将是因为空字符串是合法值而起作用。似乎许多人忽略了 replace（CharSequence，CharSequence）实际上对字符串参数起作用的事实：）

If you just exchange single for double quotes, this will work because an empty string is a legal value. It seems that many people overlook the fact that replace(CharSequence, CharSequence) actually works on string arguments :)