计算工作时间和工作时间在Java中的OverTime Hrs

Question

我有从jtextfield获得的时间字符串作为intime和我从数据库获得的第二个字符串想要计算totoal duty hrs和OverTime hrs并将其发送到java中的数据库

 stm=con.createStatement();rs = stm.executeQuery("Select * from InOut where  Token_No='"+jTextField1.getText()+"'");
 if(rs.next())
  { 
   String intime = rs.getString("In_Time");JOptionPane.showMessageDialog(null,"IN Time is '"+intime+"'"+"'");
   String outtime = jTextField2.getText();
   JOptionPane.showMessageDialog(null,"Out Time is '"+outtime+"'"+"'");

请指导......