Java资源清册-如何使用FileInputStream读取文件？

在本学期的最后一个作业中，我必须创建一个包含项目对象数组的库存程序。每个项目都包含一个ID（在添加项目时分配，不能修改）、名称、说明、现有项目数量和单价

我还需要使用文件I/O流保存和加载文件。我可以很好地保存到文本文件中。但是，我在开始使用readFile方法时遇到了问题。我真的想在不寻求任何帮助的情况下完成这项任务，但我被难住了。如何使用FileInputStream读取文本文件

项目类别

import java.text.NumberFormat;

public class Item
{
    private int ID;
    private String name;
    private String Desc;
    private int onHand;
    private double unitPrice;

    public Item(int pID)
    {
        ID = pID;
    }

    public Item(int pID, String pName, String pDesc, int pOnHand, Double pUnitPrice)
    {
        ID = pID;
        name = pName;
        Desc = pDesc;
        onHand = pOnHand;
        unitPrice = pUnitPrice;
    }

    public void display()
    {
        NumberFormat dollars = NumberFormat.getCurrencyInstance();
        System.out.printf("%-6s%-20s%-24s%-12s%-6s\n", ID, name, Desc, onHand, dollars.format(unitPrice));
    }

    // GETTERS AND SETTERS
    public int getID()
    {
        return ID;
    }

    public void setName(String pName)
    {
        name = pName;
    }

    public String getName()
    {
        return name;
    }

    public void setDesc(String pDesc)
    {
        Desc = pDesc;
    }

    public String getDesc()
    {
        return Desc;
    }

    public void setOnHand(int pOnHand)
    {
        onHand = pOnHand;
    }

    public int getOnHand()
    {
        return onHand;
    }
    public void setUnitPrice(double pUnitPrice)
    {
        unitPrice = pUnitPrice;
    }

    public double getUnitPrice()
    {
        return unitPrice;
    }

}

存货类别

import java.util.Scanner;
import java.io.PrintWriter;
import java.io. FileOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class Inventory
{
    int max = 30;
    int count = 0;
    Item myItem[] = new Item[max];
    Scanner scannerObject = new Scanner(System.in);

    public void addItem()
    {
        try{
            if (count >= max)
            {
                System.out.println("\nNo more room!");
            }else{
                System.out.print("\nPlease enter name of item: ");
                String lname = scannerObject.nextLine();
                System.out.print("\nPlease enter a brief description of the item: ");
                String ldesc = scannerObject.nextLine();
                System.out.print("\nPlease enter the amount on hand: ");
                int lonHand = scannerObject.nextInt();
                System.out.print("\nPlease enter unit price of the item: $");
                Double lunitPrice = scannerObject.nextDouble();
                myItem[count] = new Item(count + 1, lname, ldesc, lonHand, lunitPrice);
                count++;
                System.out.println("\nThank you. The ID number for " + lname + " is " + count);
                scannerObject.nextLine();
            }
        }catch(Exception e)
        {
            System.out.println("\nERROR! Please try again:\n");
            scannerObject.nextLine();
        }

    }

    public int findItem()
    {
        int found = -1;
        int inputID =0;
        try{
            System.out.print("\nGreetings, please enter the ID number for item:\n");
            inputID = scannerObject.nextInt();
            for(int i = 0; i < count; i++){
                if(myItem[i].getID() == inputID){
                    found = i;
                    scannerObject.nextLine();
                }
            }
        }catch(Exception e)
        {
            System.out.println("\nERROR!");
            scannerObject.nextLine();
        }
        return found;
    }

    public void modify()
    {
        int lfound = findItem();
        if (lfound == -1){
            System.out.println("\nInvalid input! Please try again:");
            scannerObject.nextLine();
        }else{
            try{
                System.out.print("\nPlease enter name of item: ");
                String lname = scannerObject.nextLine();
                myItem[lfound].setName(lname);
                System.out.print("\nPlease enter a brief description of the item: ");
                String ldesc = scannerObject.nextLine();
                myItem[lfound].setDesc(ldesc);
                System.out.print("\nPlease enter the amount on hand: ");
                int lonHand = scannerObject.nextInt();
                myItem[lfound].setOnHand(lonHand);
                System.out.print("\nPlease enter unit price of the item: $");
                double lunitPrice = scannerObject.nextDouble();
                myItem[lfound].setUnitPrice(lunitPrice);
                scannerObject.nextLine();
            }catch (Exception e)
            {
                System.out.println("\nInvalid command! Please try again: ");
                scannerObject.nextLine();
            }
        }
    }

    public void displayAll()
    {   System.out.println("_______________________________________________________________________________\n");
        System.out.println("                                 Inventory                                     ");
        System.out.println("_______________________________________________________________________________\n");
        System.out.printf("\n%-6s%-20s%-24s%-12s%-6s\n", "ID:", "Name:", "Description:","On Hand:", "Unit Price:\n"); //Header
        System.out.println("_______________________________________________________________________________\n");
        for(int i = 0; i < count; i++){
            myItem[i].display();
        }
    }

    public void displayOne()
    {
        int lfound = findItem();
        if (lfound == -1){
            System.out.println("\nInvalid input! Please try again:");
        }else{
            System.out.println("_______________________________________________________________________________\n");
            System.out.println("                                 Inventory                                     ");
            System.out.println("_______________________________________________________________________________\n");
            System.out.printf("\n%-6s%-20s%-24s%-12s%-6s\n", "ID:", "Name:", "Description:","On Hand:", "Unit Price:\n"); //Header
            System.out.println("_______________________________________________________________________________\n");
            myItem[lfound].display();
        }
    }

    public void saveFile()
    {
        PrintWriter outputStream = null;
        try{
            outputStream =
                new PrintWriter(new FileOutputStream("H:\\Java\\saveFile.txt"));
        }catch (FileNotFoundException e)
        {
            System.out.println("Error!");

        }
        if(outputStream != null)
            for(int i = 0; i < count; i++){
                outputStream.println(myItem[i].getID());
                outputStream.println(myItem[i].getOnHand());
                outputStream.println(myItem[i].getUnitPrice());
                outputStream.println(myItem[i].getName());
                outputStream.println(myItem[i].getDesc());
            }
        outputStream.close();
    }
}

根据我的指导老师的说法，我需要在库存类中使用保存和读取文件的方法。我需要在我的用户类中调用它们。虽然我的Item ID变量有一个“getter”，但不允许使用“setter”

---

我对Java还是相当陌生的，所以请原谅任何新手的错误。再次感谢您的帮助！我查了一下我的书，用谷歌搜索了一些例子，但我找不到任何与我的情况相关的东西

要使用FileInputStream读取文件，只需使用：

Scanner input = new Scanner(new FileInputStream("path_to_file"));

使用扫描仪读取数据的方法

while(input.hasNextLine()) { //or hasNextInt() or whatever you need to extract
  input.nextLine() //... read in a line of text from the file
}

如果希望使用文件类方法执行任何文件操作，也可以使用文件类

File myTextFile = new File("path_to_file");
Scanner input = new Scanner(new FileInputStream(myTextFile));

当然，您需要捕获

FileNotFoundException

否则，这和你为PrintWriter所做的一样。 只需将

FileOutputStream

切换为

FileInputStream

，将

PrintWriter

切换为

Scanner

，但不要忘记在从文件写入或读取切换时先关闭文件：

input.close() // or output.close()

---

我建议您使用分隔符，如

、

或空格来分隔文本文件中的数据（用于单个用户的信息）。然后使用新行分隔每个用户的条目。很好！我实际上正在考虑这样做，但不确定。然后您可以使用scanner类中的

usedimiter（）

方法。好的，我知道您在做什么。但是，我如何将这些分配给适当的变量呢？例如，将ID#分配给ID变量，将Name分配给Name变量等等？在从文本文件读回数据时，您很可能会创建

项的新实例，将从文本文件检索到的值传递到构造函数或使用适当的setter方法。嗯，您可以说newitem（input.nextInt（），input.next（），input.next（），input.nextInt（），input.nextDouble（））；但要做到这一点，您应该确保文本文件中的每一项都在单独的一行中，每一条数据都按照构造器的正确顺序排列（或者让构造器按照文本文件中的正确顺序排列）
input.close() // or output.close()