Java RS仅返回1行

我仍然对下面的代码有问题。基本上，我希望将用户输入的depID与数据库中的depID进行比较，如果找到，则更新数据，如果没有，则显示错误：

      try{
         String value1 = txt_depID.getText();
         String value2 = txt_depName.getText();

        String sql = "Update tblDepartment set depID = '"+value1+"' , depName = '"+value2+"' where depID = '"+value1+"'";
        String sql1 = "Select depID, depName from tblDepartment";
        Class.forName(driver);
        conn = DriverManager.getConnection(url);

        ps = conn.prepareStatement(sql1);
        rs = ps.executeQuery();
        ps = conn.prepareStatement(sql);
        ps.execute();


        while(rs.next()){
            String depi = rs.getString("depID"); //Issue: only reading first row

            if(depi.equals(value1)){
                JOptionPane.showMessageDialog(null, "Entry Saved");
           }

           else{
                JOptionPane.showMessageDialog(null, "Department doesn't exist");
           }
        }           
     } catch (Exception e){
         JOptionPane.showMessageDialog(null, e);
     }