Java project,every parameters is correct,but it can't connect the MySql database! [Have solved]

java project , it work first, but it doesn't work suddenly.  find code under:

　　connection = (Connection) DriverManager.getConnection(url, username, password);

the connection is null.

last find reason:

      I stop my Local Area Connection.  set is run ... the problem is solved.

转载于:https://www.cnblogs.com/gnface/archive/2012/06/05/2536490.html