Refactoring Java code etc -

okay, i'll honest: schoolwork. it's not i'm lazy, i've studies soooo , hard, still can't grip of language.. :(

it's introduction online-course, have noone talk irl.

i'm trying make program car mechanic register incoming vehicles, save objects arraylist , when user doesn't wanna register more vehicles, program read list , write out. feature have included user able search regnr , information vehicle.

the assignment partly take code below made in assignment, , refactor classes, objects, methods etc , think if that, i'll figure rest out.

    public static void main(string[] args) throws ioexception {  //write list.txt //           file myfile = new file("list.txt");         filewriter myfilewriter = new filewriter(myfile, true);         printwriter myprintwriter = new printwriter(myfilewriter);          string regnr;         string nr;         int year;         string inyear;         string model;         string name;         string date;         string indate;         int meter;         int time;         string size;         int quest = 0;          { // user input: regnr, year, model, first , last name//              nr = joptionpane.showinputdialog(null, "registration number: ");             regnr = nr.touppercase();              inyear = joptionpane.showinputdialog(null, "year of manufacture: ");             year = integer.parseint(inyear);              model = joptionpane.showinputdialog(null, "model: ");              name = joptionpane.showinputdialog(null, "owner: ");  // todays date //              indate= calendar.getinstance().gettime().tostring();             date = indate.substring(0, 10);                                //substring day : month : date  // expected service time through .random //              double min = 1500 + math.random();             double max = math.random() * (40000 - min);             double number = min + max;              meter = (int) number;             time = meter / 1500;  // recommended service size//              if (meter <= 8000) {                 size = "a small service recommended.";             } else if (meter > 8000 && meter <= 20000) {                 size = "a medium size service recommended";             } else {                 size = "a large service recommended";             }              myprintwriter.println("car: " + model + " " + regnr);             myprintwriter.println("year of manufacture: " + year);             myprintwriter.println("owner: " + name);             myprintwriter.println("meter: " + meter + " mil");             myprintwriter.println("start date: " + date);             myprintwriter.println("expected time: " + time + " dagar \n" + size);             myprintwriter.println("\n");              quest = joptionpane.showconfirmdialog(null, "do want continue?");         } while (quest != 1);          myprintwriter.close();  // read list.txt //          try (bufferedreader br = new bufferedreader(new filereader("list.txt"))) {             stringbuilder sb = new stringbuilder();             string line = br.readline();              while (line != null) {                 sb.append(line);                 sb.append(system.lineseparator());                 line = br.readline();             }             string list = sb.tostring();             br.close();              joptionpane.showmessagedialog(null, list);          }     } } 

i've refactored code, split 4 classes. car, userinteraction, fileinteraction , entrypoint.

car holding information. registrationnumber, model, owner , on. used getters there.

public class car{      private final string registrationnumber;     private final int manufactureyear;     private final string model;     private final string date;     private final string owner;     private final int drivenmeters;     private final string servicelevel;      public car( string registrationnumber, int manufactureyear, string model, string owner, int drivenmeters, string servicelevel, string date ){         this.registrationnumber = registrationnumber;         this.manufactureyear = manufactureyear;         this.model = model;         this.owner = owner;         this.drivenmeters = drivenmeters;         this.servicelevel = servicelevel;         this.date = date;     }      public string getregistrationnumber(){         return registrationnumber;     }      public int getmanufactureyear(){         return manufactureyear;     }      public string getmodel(){         return model;     }      public string getdate(){         return date;     }      public string getowner(){         return owner;     }      public int getdrivenmeters(){         return drivenmeters;     }      public string getservicelevel(){         return servicelevel;     } } 

userinteraction layer between application , user using it. asks user input values. displays message if wants continue , displays cars registered.

import javax.swing.*; import java.util.calendar;  public class userinteraction{      public static car fillcarwithuserinput(){         // ask user values         final string model =             joptionpane.showinputdialog(null, "model: ");         final string registrationnumber =             joptionpane.showinputdialog(null, "registration number: ").touppercase();         final int manufactureyear =             integer.parseint(joptionpane.showinputdialog(null, "year of manufacture: "));         final string owner =             joptionpane.showinputdialog(null, "owner: ");          // randomly generate meters         double min = 1500 * math.random();         double max = math.random() * (40000 - min);         final int drivenmeters = (int) (min + max);          // determine service level         final string servicelevel;         if( drivenmeters <= 8000 ){             servicelevel = "a small service recommended.";         } else if( drivenmeters <= 20000 ){             servicelevel = "a medium size service recommended";         } else{             servicelevel = "a large service recommended";         }          // today date         final string date = calendar.getinstance().gettime().tostring().substring(0, 10);          // return new car object containing values         return new car(registrationnumber, manufactureyear, model, owner, drivenmeters, servicelevel, date);     }      public static boolean userwantstocontinue(){         return joptionpane.showconfirmdialog(null, "do want continue?") != 1;     }      public static void showcarstouser( string cars ){         joptionpane.showmessagedialog(null, cars);     } } 

fileinteraction layer between application , filesystem. writes list.txt reads it.

import java.io.*; import java.util.objects; import java.util.stream.collectors;  public class fileinteraction implements closeable{      private static final string filename = "list.txt";      private printwriter writer;      public void printcar( car car ) throws ioexception{         // lazily initialize writer         if( writer == null ){             writer = new printwriter(new filewriter(filename, true));         }         writer.println("car: " + car.getmodel() + " " + car.getregistrationnumber());         writer.println("year of manufacture: " + car.getmanufactureyear());         writer.println("owner: " + car.getowner());         writer.println("meter: " + car.getdrivenmeters() + " mil");         writer.println("start date: " + car.getdate());         writer.println("expected time: " + car.getdrivenmeters() / 1500 + " dagar \n" + car.getservicelevel());         writer.println("\n");     }      public string readcars(){         // read cars file         string carlist;         try( bufferedreader reader = new bufferedreader(new filereader(filename)) ){             // following 3 lines new java8 called stream quite handy             carlist = reader.lines() // returns lines stream                 .filter(objects::nonnull) // eliminates null values                 .collect(collectors.joining("\n")); // appends lines         } catch( ioexception e ){             // print stack             e.printstacktrace();             // if exception occurs assing empty string             carlist = "";         }          return carlist;     }      @override     public void close() throws ioexception{         if( writer != null ){             writer.flush();             writer.close();         }     } } 

and entrypoint used bring together. name states entrypoint application. class done.

import java.io.ioexception;  public class entrypoint{      public static void main( string[] args ){         try( fileinteraction fileinteraction = new fileinteraction() ){             do{                 final car car = userinteraction.fillcarwithuserinput();                 fileinteraction.printcar(car);             } while( userinteraction.userwantstocontinue() );              string cars = fileinteraction.readcars();             userinteraction.showcarstouser(cars);         } catch( ioexception e ){             // print stack             e.printstacktrace();             // exit application             throw new illegalstateexception("encountered exception!", e);         }     } } 

this quite load of work, hope helps you. if have done maybe can inspired this.