java 连接MYSQL 进行查询怎么修改

Question

importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.Statement;publicclassshiyan4{ publicstaticfinalStringDBDRIVER="org.gjt.mm.mysql.Driver"; publicstaticfinalStringDBURL="jdbc:mysql://localhost:3306/ace"; publicstaticfinalStringDBUSER="root"; publicstaticfinalStringDBPASS="root"; publicstaticvoidmain(Stringargs[])throwsException{ Connectionconn=null; Statementstmt=null; Class.forName(DBDRIVER); Stringsql="SELECTuser_nameFROMusers;"; conn=DriverManager.getConnection(DBURL,DBUSER,DBPASS); stmt=conn.createStatement(); stmt.executeUpdate(sql); stmt.close(); conn.close(); }}请问这样怎么修改才能正常的进行查询和在java上输出查询到的信息