Java Как загрузить txtfile с помощью objectinputstream

Question

Heres wat Ive, сделанный до сих пор, я использую hashmap. Я уже сохранил файл с помощью objectoutputstream и сохранил его как файл txt. Теперь я хочу загрузить то, что я сохранил, когда снова открываю свою программу, используя objectinputstream Является ли это возможным? например, я ввел Item 1 = ID: 1, Name: Apple, Price: 30 после ввода, я сохраняю его, затем закройте программу. Если я открою программу, то pres [4] - для списка всех элементов на карте появится элемент 1.

public static void main(String[] args) { 
    Scanner s = new Scanner(System.in); 
    HashMap<Integer, Item> items = new HashMap<>(); 
    Set<Integer> keys = items.keySet(); 
    while (true) { 
     boolean exist = true; 
     lineBreak(12, " -"); 
     System.out.println("|***ITEM MANAGEMENT***|"); 
     System.out.println("| [1] - Add Item  |"); 
     System.out.println("| [2] - Delete Item |"); 
     System.out.println("| [3] - Edit Item  |"); 
     System.out.println("| [4] - List All Items|"); 
     System.out.println("| [5] - View Item  |"); 
     System.out.println("| [6] - Save   |"); 
     System.out.println("| [7] - Exit   |"); 
     lineBreak(12, " -"); 
     System.out.print("Enter your choice>> "); 
     int choice = s.nextInt(); 
     int id; 
     String name, des; 
     float price; 
     Item i; 
     switch (choice) { 
      case 1: 
       System.out.print("INPUT ID: "); 
       id = s.nextInt(); 
       if(items.containsKey(id) == exist){System.out.println("This id already exist"); 
       exist = false; 
       break; 
       } 
       if(exist == true){ 
       s.nextLine(); //trap 
       System.out.print("INPUT NAME: "); 
       name = s.nextLine(); 
       System.out.print("INPUT DESCRIPTION: "); 
       des = s.nextLine(); 
       System.out.print("INPUT PRICE: "); 
       price = s.nextFloat(); 
       i = new Item(name, des, price); 
       items.put(id, i); 
       } 
       break; 
      case 2: 
       System.out.println("ENTER ID: "); 
       id = s.nextInt(); 
       if (items.get(id) == null) { 
        System.out.println("This id does not exist\n"); 
       } else { 
        items.remove(id); 
       } 
       break; 
      case 3: 
       System.out.println("ENTER ID: "); 
       id = s.nextInt(); 
       if (items.get(id) == null) { 
        System.out.println("This id does not exist"); 
       } else { 
        s.nextLine(); //trap 
        System.out.print("INPUT NEW NAME: "); 
        name = s.nextLine(); 
        System.out.print("INPUT NEW DESCRIPTION: "); 
        des = s.nextLine(); 
        System.out.print("INPUT NEW PRICE: "); 
        price = s.nextFloat(); 
        i = new Item(name, des, price); 
        items.replace(id, i); 
       } 
       break; 
      case 4: 
       System.out.printf("%-15s%-8s%15s\n", "ID", "NAME", "PRICE"); 
       lineBreak(19, " -"); 
       if (items.isEmpty()) { 
        System.out.printf("\n%-12s%-15s%15s\n\n", "", "NORECORDSTOSHOW", ""); 
       } else { 
        for (int key : keys) { 
         System.out.printf("%-15d%15s\n", key, items.get(key).itemInfo()); 
        } 
        System.out.println(); 
       } 
       break; 
      case 5: 
       System.out.println("ENTER ID: "); 
       id = s.nextInt(); 
       if (items.get(id) == null) { 
        System.out.println("This id does not exist\n"); 
       } else { 
        System.out.printf("%-15s%-15s%-15s%15s\n", "ID", "NAME", "DESCRIPTION", "PRICE"); 
        System.out.printf("%-15d%15s\n\n", id, items.get(id).viewitem()); 
       } 
       break; 
      case 6: 
       String file ="c:\\prespres.txt"; 
     try { 
      FileOutputStream fos = new FileOutputStream(file); 
      ObjectOutputStream oos = new ObjectOutputStream(fos); 
      oos.writeObject(items); 
      oos.close(); 
      fos.close(); 
      System.out.println("SAVED!"); 
     } catch (FileNotFoundException ex) { 
      Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); 
     } catch (IOException ex) { 
      Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); 
     } 
       break; 
      case 7: 
       System.exit(1); 
      default: 
       System.out.println("Invalid Input!\n"); 
     } 
    } 

}re 

Answer 1

Вы можете использовать ObjectInputStream читать объект

private static HashMap<Integer, Item> readItems() { 
    HashMap<Integer, Item> items = null; 
    try { 
     FileInputStream fin = new FileInputStream("c:\\prespres.txt"); 
     ObjectInputStream ois = new ObjectInputStream(fin); 
     items = (HashMap<Integer, Item>) ois.readObject(); 
     ois.close(); 
    } catch (Exception ex) {} 
    return (items == null) ? new HashMap<>() : items; 
} 

Изменить добавить этот метод для чтения карты при запуске. У меня нет всего кода, но полный образец будет похож на

import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.io.Serializable; 
import java.util.HashMap; 
import java.util.Scanner; 
import java.util.Set; 
import java.util.logging.Level; 
import java.util.logging.Logger; 


class Item implements Serializable{ 
    String name; 
    String description; 
    float price; 

    public Item(String name, String description, float price) { 
     this.name = name; 
     this.description = description; 
     this.price = price; 
    } 

    public String getName() { 
     return name; 
    } 
    public void setName(String name) { 
     this.name = name; 
    } 
    public String getDescription() { 
     return description; 
    } 
    public void setDescription(String description) { 
     this.description = description; 
    } 
    public float getPrice() { 
     return price; 
    } 
    public void setPrice(float price) { 
     this.price = price; 
    } 

    @Override 
    public String toString() { 
     return "Item [name=" + name + ", description=" + description 
       + ", price=" + price + "]"; 
    } 

    public String itemInfo() { 
     return toString(); 
    } 

    public String viewitem() { 
     return toString(); 
    } 
} 

public class FileReader { 

    public static void main(String[] args) { 
     Scanner s = new Scanner(System.in); 
     HashMap<Integer, Item> items = readItems(); 
     Set<Integer> keys = items.keySet(); 
     while (true) { 
     boolean exist = true; 
     lineBreak(12, " -"); 
     System.out.println("|***ITEM MANAGEMENT***|"); 
     System.out.println("| [1] - Add Item  |"); 
     System.out.println("| [2] - Delete Item |"); 
     System.out.println("| [3] - Edit Item  |"); 
     System.out.println("| [4] - List All Items|"); 
     System.out.println("| [5] - View Item  |"); 
     System.out.println("| [6] - Save   |"); 
     System.out.println("| [7] - Exit   |"); 
     lineBreak(12, " -"); 
     System.out.print("Enter your choice>> "); 
     int choice = s.nextInt(); 
     int id; 
     String name, des; 
     float price; 
     Item i; 
     switch (choice) { 
      case 1: 
      System.out.print("INPUT ID: "); 
      id = s.nextInt(); 
      if(items.containsKey(id) == exist){System.out.println("This id already exist"); 
      exist = false; 
      break; 
      } 
      if(exist == true){ 
      s.nextLine(); //trap 
      System.out.print("INPUT NAME: "); 
      name = s.nextLine(); 
      System.out.print("INPUT DESCRIPTION: "); 
      des = s.nextLine(); 
      System.out.print("INPUT PRICE: "); 
      price = s.nextFloat(); 
      i = new Item(name, des, price); 
      items.put(id, i); 
      } 
      break; 
      case 2: 
      System.out.println("ENTER ID: "); 
      id = s.nextInt(); 
      if (items.get(id) == null) { 
       System.out.println("This id does not exist\n"); 
      } else { 
       items.remove(id); 
      } 
      break; 
      case 3: 
      System.out.println("ENTER ID: "); 
      id = s.nextInt(); 
      if (items.get(id) == null) { 
       System.out.println("This id does not exist"); 
      } else { 
       s.nextLine(); //trap 
       System.out.print("INPUT NEW NAME: "); 
       name = s.nextLine(); 
       System.out.print("INPUT NEW DESCRIPTION: "); 
       des = s.nextLine(); 
       System.out.print("INPUT NEW PRICE: "); 
       price = s.nextFloat(); 
       i = new Item(name, des, price); 
       items.replace(id, i); 
      } 
      break; 
      case 4: 
      System.out.printf("%-15s%-8s%15s\n", "ID", "NAME", "PRICE"); 
      lineBreak(19, " -"); 
      if (items.isEmpty()) { 
       System.out.printf("\n%-12s%-15s%15s\n\n", "", "NORECORDSTOSHOW", ""); 
      } else { 
       for (int key : keys) { 
       System.out.printf("%-15d%15s\n", key, items.get(key).itemInfo()); 
       } 
       System.out.println(); 
      } 
      break; 
      case 5: 
      System.out.println("ENTER ID: "); 
      id = s.nextInt(); 
      if (items.get(id) == null) { 
       System.out.println("This id does not exist\n"); 
      } else { 
       System.out.printf("%-15s%-15s%-15s%15s\n", "ID", "NAME", "DESCRIPTION", "PRICE"); 
       System.out.printf("%-15d%15s\n\n", id, items.get(id).viewitem()); 
      } 
      break; 
      case 6: 
      String file ="c:\\prespres.txt"; 
       try { 
        FileOutputStream fos = new FileOutputStream(file); 
        ObjectOutputStream oos = new ObjectOutputStream(fos); 
        oos.writeObject(items); 
        oos.close(); 
        fos.close(); 
        System.out.println("SAVED!"); 
       } catch (FileNotFoundException ex) { 
        Logger.getLogger(FileReader.class.getName()).log(Level.SEVERE, null, ex); 
       } catch (IOException ex) { 
        Logger.getLogger(FileReader.class.getName()).log(Level.SEVERE, null, ex); 
       } 
      break; 
      case 7: 
      System.exit(1); 
      default: 
      System.out.println("Invalid Input!\n"); 
     } 
     } 
    } 

    private static HashMap<Integer, Item> readItems() { 
     HashMap<Integer, Item> items = null; 
     try { 
      FileInputStream fin = new FileInputStream("c:\\prespres.txt"); 
      ObjectInputStream ois = new ObjectInputStream(fin); 
      items = (HashMap<Integer, Item>) ois.readObject(); 
      ois.close(); 
     } catch (Exception ex) {} 
     return (items == null) ? new HashMap<>() : items; 
    } 

    private static void lineBreak(int i, String string) { 

    } 

}