fileclassdemo.java

java编程代码

 
import java.util.Scanner;
import java.io.File;
import java.io.PrintWriter;
import java.io.FileOutputStream;
import java.io.FileNotFoundException;
 
public class FileClassDemo
{
    public static void main(String[] args)
    {
        Scanner keyboard = new Scanner(System.in);
        String line = null;
        String fileName = null;
 
        System.out.println("I will store a line of text for you.");
        System.out.println("Enter the line of text:");
        line = keyboard.nextLine( );
 
        System.out.println("Enter a file name to hold the line:");
        fileName = keyboard.nextLine( );
        File fileObject = new File(fileName);

        while (fileObject.exists( ))
        {
            System.out.println("There already is a file named "
                                       + fileName);
            System.out.println("Enter a different file name:");
            fileName = keyboard.nextLine( );
            fileObject = new File(fileName);
        }
  
         PrintWriter outputStream = null;
         try
         {
             outputStream = 
                  new PrintWriter(new FileOutputStream(fileName));
         }
         catch(FileNotFoundException e)
         {
             System.out.println("Error opening the file " + fileName);
             System.exit(0);
         }
  
         System.out.println("Writing \""  + line + "\"");
         System.out.println("to the file "  + fileName);
         outputStream.println(line);
  
         outputStream.close( );
         System.out.println("Writing completed.");
     }
 }