Question

**我为一台简单的ATM机编写了一个程序。代码正在生成 Exception :: java.lang.UnsupportedOperationException：尚不支持。请让我摆脱这个问题。我们也不能使用exists（）函数和FileOutputStream吗？

 import java.io.*;
 import java.util.Scanner;
 class Customer1 implements Serializable
{
      private static final int serialVersionUID=100;
int i;
transient Scanner s=new Scanner(System.in); 
int acc[]=new int[5];
int pin[]=new int[5];
double balance[]=new double[5];
void getdata(int i)
{
            System.out.println("Enter account number: ");
            acc[i]=s.nextInt();
            System.out.println("Enter pin: ");
            pin[i]=s.nextInt();
            System.out.println("Enter balance: ");
            balance[i]=s.nextDouble();
}  
void showdata(int i)
{
            System.out.println("Account number is: "+acc[i]);
            System.out.println("Pin is: "+pin[i]);
            System.out.println("Balance is: "+balance[i]);
}
  }
   class WriteFile1 implements Serializable
   {
    public static final int serialVersionUID=100;
void filewrite()
    {
        try
        {
        Customer1 c=new Customer1();
        boolean f;
        File fo=new File("ATM.txt");
        FileOutputStream fout=new FileOutputStream(fo);
        if(fo.exists())
        {
             System.out.println("                       ATM     MACHINE");  
             System.out.println("Enter your ATM pin:");
             String pass=s.nextLine();
             for(int i=0;i<2;i++)
             {
                 if(pass.equals(c.pin))
                 {
                     try
                    {
                        FileInputStream fin=new FileInputStream("ATM.txt");
                        ObjectInputStream objin=new ObjectInputStream(fin);
                        Customer1 c1=(Customer1)objin.readObject();
                        c1.showdata(i);
                        fin.close();
                    }
                    catch(Exception e)
                    {
                        System.out.println("Exception:: "+e.getMessage());
                    }
                 }
             }
        }
        else
        {
            f=fo.createNewFile();
        }
        ObjectOutputStream objout=new ObjectOutputStream(fout);
        for(int i=0;i<2;i++)
        {
            c.getdata(i);
        }
        objout.writeObject(c);
        fout.close();
        objout.close();
        }
    catch(Exception e)
    {
        System.out.println("Exception :: "+e);
    }
    }
  }
     public class project
     {
void mainmenu()
{
    System.out.println("1.   Withdraw Cash.");
    System.out.println("2.   Deposit Cash.");
    System.out.println("3.   Generate Receipt.");
    System.out.println("4.   Exit.");
}
    public static void main(String[] args)
    {
    Scanner s=new Scanner(System.in); 
    project a=new project();   
    WriteFile1 wr=new WriteFile1();
    wr.filewrite();
   }
 }

Answer 1

在WriteFile1类中还添加一个Scanner变量

class WriteFile1 implements Serializable {

    transient Scanner s = new Scanner(System.in);

    //your other code

}

关于FileOutputStream的问题。如果文件不存在并且无法创建它，它将抛出异常。

来自javadoc： FileNotFoundException - 如果文件存在但是是目录而不是常规文件，则不存在但无法创建，或者由于任何其他原因无法打开

Exception :: java.lang.UnsupportedOperationException：尚不支持

1 个答案: