在Java中寫入二進制文件

Question

我正在製作一個使用兩個數組列表的程序。我研究瞭如何將對象寫入二進制文件，並試圖實現它，但它永遠不能正常工作。我需要能夠運行程序創建文件，然後寫入文件，當我想保存。下一次加載程序時，它需要能夠讀取數組列表。我已經在我存儲的兩個對象中實現了Serializable。

import java.util.ArrayList; 

import java.util.Scanner; 

import java.io.*; 

//Add person functionality next 
public class main { 
    ArrayList<Person> people = new ArrayList<Person>(); 
    ArrayList<Date> dates = new ArrayList<Date>(); 

    //Possibly add a checkExistence Function somewhere 
    //Otherwise self explanatory 
    public boolean newPerson(){ 
     Scanner kbd = new Scanner(System.in); 

     String input = ""; 
     boolean nameIsCorrect = false; 
     boolean typeIsCorrect = false; 
     do{ 
      boolean nameContinue = false; 
      while(!nameContinue){ 
       System.out.println("What is the name?"); 
       input = kbd.nextLine(); 
       nameContinue = yesOrNo(); 
       if(nameContinue){ 
        nameContinue = checkForExistence(input); 
        if(!nameContinue){ 
         System.out.println("Name already exists, try again"); 
        } 
       } 
      } 
      String[] tokens = input.split(" "); 
      if(tokens.length == 1){ 
       String name = tokens[0]; 
       String type = ""; 
       do{ 
        System.out.println("What type? F (Family) P (Punch) S (Season)"); 
        input = kbd.nextLine(); 
        if(input.equalsIgnoreCase("f")){ 
         type = "f"; 
         typeIsCorrect = true; 
         nameIsCorrect = true; 
        } 
        else if(input.equalsIgnoreCase("s")){ 
         type = "s"; 
         typeIsCorrect = true; 
         nameIsCorrect = true; 
        } 
        else if(input.equalsIgnoreCase("p")){ 
         type = "p"; 
         typeIsCorrect = true; 
         nameIsCorrect = true; 
        } 
        else{ 
         System.out.println("Invalid, try again"); 
        } 
       } while(!typeIsCorrect); 
       Person np = new Person(name, type); 
       people.add(np); 
       System.out.println(np.getName() + " added!"); 
      } 
      else{ 
       System.out.println("Not correct format let's try again"); 
      } 
     } while(!nameIsCorrect); 
     return true; 
    }//End of newPerson function 

    //Cycles through and prints a roster 
    public boolean printPeopleList(){ 
     for(int i = 0; i < people.size(); i++){ 
      System.out.println(people.get(i).getName()); 
     } 
     return true; 
    } 

    //Testing for valid input 
    public boolean testDateValidity(String input, int which){ 
     if(which == 1){ 
      String[] dates = new String[21]; 
      int count = 0; 
      for(int i = 1; i <= 12; i++){ 
       if(i < 10){ 
        dates[count] = "0" + Integer.toString(i); 
        count++; 
       } 
       dates[count] = Integer.toString(i); 
       count++; 
      } 

      for(int j = 0; j < dates.length; j++){ 
       if(input.equalsIgnoreCase(dates[j])){ 
        return true; 
       } 
      } 
     } 
     else if(which == 2){ 
      String[] dates = new String[40]; 
      int count = 0; 
      for(int i = 1; i <= 31; i++){ 
       if(i < 10){ 
        dates[count] = "0" + Integer.toString(i); 
        count++; 
       } 
       dates[count] = Integer.toString(i); 
       count++; 
      } 

      for(int j = 0; j < dates.length; j++){ 
       if(input.equalsIgnoreCase(dates[j])){ 
        return true; 
       } 
      } 
     } 
     else{ 
      return false; 
     } 

     return false; 
    } 

    //Cycles through and prints all dates and their attendance 
    public boolean printListOfDates(){ 
     System.out.println("Date\tPeople"); 
     for(int i = 0; i < dates.size(); i++){ 
      System.out.println(dates.get(i).toString()); 
     } 
     return true; 
    } 

    public boolean printCurrentPeople(int day){ 
     dates.get(day).printList(); 
     return true; 
    } 

    //Returns the day position from the ArrayList 
    public int findDayPosition(String month, String day){ 
     for(int i = 0; i < dates.size(); i++){ 
      if(month.equalsIgnoreCase(dates.get(i).getMonth()) && day.equalsIgnoreCase(dates.get(i).getDay())){ 
       return i; 
      } 
     } 

     return -1; 
    } 

    public boolean addVisit(String name, int date){ 
     for(int i = 0; i < people.size(); i++){ 
      if(people.get(i).getName().equalsIgnoreCase(name)){ 
       people.get(i).incrementVisits(); 
       people.get(i).addDay(dates.get(date).toStringPerson()); 
       dates.get(date).addVisitor(name); 
       return true; 
      } 
     } 
     System.out.println("Person not found"); 
     return false; 
    } 

    public boolean addVisit(String name, int visits, int date){ 
     for(int i = 0; i < people.size(); i++){ 
      if(people.get(i).getName().equalsIgnoreCase(name)){ 
       people.get(i).incrementVisits(visits); 
       dates.get(date).addVisitor(name, visits); 
       people.get(i).addDay(dates.get(date).toStringPerson(), visits); 
       return true; 
      } 
     } 
     System.out.println("Person not found"); 
     return false; 
    } 

    public boolean regAdd(int date){ 
     dates.get(date).addRegular(); 
     return true; 
    } 

    public boolean regAdd(int date, int visits){ 
     dates.get(date).addRegular(visits); 
     return true; 
    } 

    public boolean helpFunction(){ 
     File fin = new File("help.txt"); 
     if(!fin.exists()){ 
      System.out.println("I'm sorry the help file has become corrupted :("); 
      System.out.println("Please contact the maker of this program to fix it"); 
      System.out.println("Upon contact he will probably let out a loud UGH"); 
     } 
     else{ 
      try{ 
       FileReader fr = new FileReader(fin); 
       BufferedReader br = new BufferedReader(fr); 
       String line; 
       while((line = br.readLine()) != null){ 
        System.out.println(line); 
       } 
      } catch (FileNotFoundException fnf) { 
       //This line is completely pointless as the if function above serves its purpose 
       System.out.println("File was not found"); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 


     } 
     return true; 
    } 

    public boolean checkExistence(String name){ 
     for(int i = 0; i < people.size(); i++){ 
      if(people.get(i).getName().equalsIgnoreCase(name)){ 
       return true; 
      } 
     } 
     return false; 
    } 

    public int getPersonPosition(String name){ 
     for(int i = 0; i < people.size(); i++){ 
      if(people.get(i).getName().equalsIgnoreCase(name)){ 
       return i; 
      } 
     } 
     return -1; 
    } 

    public boolean printPersonDates(String name){ 
     int x = getPersonPosition(name); 
     people.get(x).printDates(); 
     return true; 
    } 


    public String changeMonth(){ 
     Scanner kbd = new Scanner(System.in); 
     String input; 
     boolean continueProgram = false; 
     boolean monthContinue = false; 
     //Recieve the date 
     do{ 
      System.out.println("What is the month?"); 
      input = kbd.nextLine(); 
      monthContinue = testDateValidity(input, 1); 
      if(monthContinue){ 
       continueProgram = true; 
      } 
     } while (!continueProgram); 
     String month = input; 
     return month; 
    } 

    public String changeDay(){ 
     Scanner kbd = new Scanner(System.in); 
     String input; 
     boolean continueProgram = false; 
     boolean dayContinue = false; 
     //Recieve the date 
     do{ 
      System.out.println("What is the day?"); 
      input = kbd.nextLine(); 
      dayContinue = testDateValidity(input, 2); 
      if(dayContinue){ 
       continueProgram = true; 
      } 
     } while (!continueProgram); 
     String day = input; 
     return day; 
    } 

    public boolean yesOrNo(){ 
     Scanner kbd = new Scanner(System.in); 
     String input; 
     do{ 
      System.out.println("Are you sure? Y or N"); 
      input = kbd.nextLine(); 
     } while(!checkYes(input)); 
     if(input.equalsIgnoreCase("y") || input.equalsIgnoreCase("yes")){ 
      return true; 
     } 
     else if(input.equalsIgnoreCase("n") || input.equalsIgnoreCase("no")){ 
      return false; 
     } 
     else{ 
      return false; 
     } 
    } 

    public boolean checkYes(String input){ 
     if(input.equalsIgnoreCase("y") || input.equalsIgnoreCase("yes")){ 
      return true; 
     } 
     else if(input.equalsIgnoreCase("n") || input.equalsIgnoreCase("no")){ 
      return true; 
     } 
     else{ 
      return false; 
     } 
    } 

    public boolean checkForExistence(String input){ 
     for(int i = 0; i < people.size(); i++){ 
      if(input.equalsIgnoreCase(people.get(i).getName())){ 
       return false; 
      } 
     } 
     return true; 
    } 
    //Main Function 
    public static void main(String[] args){ 
     main pool = new main(); 
     Scanner kbd = new Scanner(System.in); 
     String input; 
     int numberData; 
     boolean continueProgram = false; 
     String month; 
     String day; 
     int dayPosition; 
     String dateString; 

     System.out.println("Welcome to the Pool Database Management System"); 
     System.out.println("Copyright 2011 by Dalton Dick"); 

     boolean monthContinue = false; 
     //Recieve the date 
     do{ 
      System.out.println("What is the month?"); 
      input = kbd.nextLine(); 
      monthContinue = pool.testDateValidity(input, 1); 
      if(monthContinue){ 
       continueProgram = true; 
      } 
     } while (!continueProgram); 
     month = input; 

     continueProgram = false; 
     boolean dayContinue = false; 
     //Recieve the date 
     do{ 
      System.out.println("What is the day?"); 
      input = kbd.nextLine(); 
      dayContinue = pool.testDateValidity(input, 2); 
      if(dayContinue){ 
       continueProgram = true; 
      } 
     } while (!continueProgram); 
     day = input; 

     //Adding the date object or finding the date already stored 
     if(pool.findDayPosition(month, day) != -1){ 
      dayPosition = pool.findDayPosition(month, day); 
      System.out.println("Date already exists, using."); 
     } 
     else{ 
      Date dayObject = new Date(month, day); 
      pool.dates.add(dayObject); 
      dayPosition = pool.findDayPosition(month, day); 
      System.out.println("Date added"); 
     } 

     continueProgram = true; 
     boolean needsAFunction = true; 
     while(continueProgram){ 
      System.out.println("Please enter a command"); 
      input = kbd.nextLine(); 
      String[] tokens = input.split(" "); 

      if(tokens[0].equalsIgnoreCase("help")){ 
       if(tokens.length == 1){ 
        pool.helpFunction(); 
       } 
       else{ 
        System.out.println("Invalid Command"); 
       } 
      } 
      else if(tokens[0].equalsIgnoreCase("new")){ 
       if(tokens.length == 1){ 
        pool.newPerson(); 
       } 
       else{ 
        System.out.println("Invalid Command"); 
       } 
      } 
      else if(tokens[0].equalsIgnoreCase("print")){ 
       if(tokens.length == 2){ 
        if(tokens[1].equalsIgnoreCase("people")){ 
         pool.printPeopleList(); 
        } 
        else if(tokens[1].equalsIgnoreCase("dates")){ 
         pool.printListOfDates(); 
        } 
        else if(tokens[1].equalsIgnoreCase("current")){ 
         pool.printCurrentPeople(dayPosition); 
        } 
       }//End if Statement 
       else if(tokens.length == 3){ 
        if(pool.checkExistence(tokens[1])){ 
         if(tokens[2].equalsIgnoreCase("dates")){ 
          pool.printPersonDates(tokens[1]); 
         } 
         else{ 
          System.out.println("Invalid"); 
         } 
        } 
        else{ 
         System.out.println("Person does not exist"); 
        } 

       } 
      } 
      else if(tokens[0].equalsIgnoreCase("quit") || tokens[0].equalsIgnoreCase("q") || tokens[0].equalsIgnoreCase("exit")){ 
       System.out.println("Exiting System"); 
       System.exit(0); 
      } 
      else if(tokens[0].equalsIgnoreCase("add")){ 
       if(tokens.length == 1){ 
        System.out.println("Invalid use of the command"); 
       } 
       else if(tokens.length == 2){ 
        pool.addVisit(tokens[1], dayPosition); 
       } 
       else if(tokens.length == 3){ 
        try{ 
         int x = Integer.parseInt(tokens[2]); 
         pool.addVisit(tokens[1], x, dayPosition); 
        } catch (NumberFormatException nfe){ 
         System.out.println("Not a number"); 
        }//End try catch block 
       }//End else if 
      } 
      else if(tokens[0].equalsIgnoreCase("change")){ 
       if(tokens.length == 2){ 
        if(tokens[1].equalsIgnoreCase("date")){ 
         month = pool.changeMonth(); 
         day = pool.changeDay(); 
         if(pool.findDayPosition(month, day) != -1){ 
          dayPosition = pool.findDayPosition(month, day); 
          System.out.println("Date already exists, using."); 
         } 
         else{ 
          Date dayObject = new Date(month, day); 
          pool.dates.add(dayObject); 
          dayPosition = pool.findDayPosition(month, day); 
          System.out.println("Date added"); 
         } 
        } 
        else{ 
         System.out.println("Invalid Command"); 
        } 
       } 
       else{ 
        System.out.println("Invalid Command"); 
       } 

      } 
      else if(tokens[0].equalsIgnoreCase("regular") || tokens[0].equalsIgnoreCase("reg")){ 
       if(tokens.length == 1){ 
        pool.regAdd(dayPosition); 
       } 
       else if(tokens.length == 2){ 
        try{ 
         pool.regAdd(dayPosition, Integer.parseInt(tokens[1])); 
        } catch (NumberFormatException nfe) { 
         System.out.println("Not correct input"); 
        } 
       } 

      } 
      else{ 
       System.out.println("Invalid Command"); 
      } 
     } 
    } 
} 

Answer 1

檢查this例如：

ArrayList<Student> list = new ArrayList<Student>(); 
list.add(student1); 
list.add(student2); 
list.add(student3); 

FileOutputStream fos; 
try 
{ 
    fos = new FileOutputStream(FILENAME); 
    ObjectOutputStream oos = new ObjectOutputStream(fos); 
    oos.writeObject(list); 
    // read back 
    FileInputStream fis = new FileInputStream(FILENAME); 
    ObjectInputStream ois = new ObjectInputStream(fis); 
    Object obj = ois.readObject(); 
    ArrayList<Student> listFromFile = (ArrayList) obj; 
    for (Student student: listFromFile) 
    { 
    System.out.println(student.toString()); 
    }  
} 
catch (FileNotFoundException e) 
{ 
    e.printStackTrace();   
}