java 验证邮箱

public boolean isValid(String str)
??{
???String valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.@_-";
???String temp;
???if(str == null) return false;
??????????? if(str.trim().equals("")) return false;
???for (int i=0; i < str.length(); i++)
???{
????temp = "" + str.substring(i, i+1);
????if (valid.indexOf(temp) == -1)
?????return false;
???}
???return true;
??}