从输入日志写入文件

Question

So I'm having a few troubles here. I need to be able to write my output to a file, and have it contain only the keywords specified in the code. This code is writing nothing to the file, and it only opens another box for user input. How do I get it to close the input box after the user inputs the file name, get it to write the output to the file, and get the output to display in the compiler? Thanks!

import java.util.*;
import java.io.*;

public class Classname {

   static Scanner sc = new Scanner(System.in);

   public static void main(String args[]) throws IOException, 
   FileNotFoundException {

   String filename;

   // Connecting to a file with a buffer
   PrintWriter outFile = new PrintWriter(
                          new BufferedWriter(
                           new FileWriter("chatOutput.log")));

   // Get the file
   System.out.print("Please enter full name of the file: ");
   filename = sc.next();

   // Assign the name of the text file to a file object
   File log = new File( filename);
   String textLine = null; // Null
   String outLine = "";    // Null

   while(sc.hasNext())
   {
     String line=sc.nextLine();
     if(line.contains("LANTALK"))
     System.out.println(line);
   }

   try
   {
     // assigns the file to a filereader object..this will throw an error if 
     the file does not exist or cannot be found
     BufferedReader infile = new BufferedReader(new FileReader(log));

   try
   {
     // read data from a file..this will throw and error if something goes 
     wrong reading (empty or past end of file)
     while((textLine = infile.readLine()) != null)
   {
     //System.out.printf("%s\n",textLine);
     outLine = textLine.toUpperCase();
     outFile.printf("%s\n",outLine);
   }// end of while 
   } // end of try

  finally  // finally blocks get executed even if an exception is thrown 
   {
     infile.close();
     outFile.close();
   }
   }// end of try

 catch (FileNotFoundException nf) // this goes with the first try because it 
 will throw a FileNotFound exception
   {
     System.out.println("The file \""+log+"\" was not found"); 
   }
 catch (IOException ioex) // this goes with the second try because it will 
 throw an IOexception
   {
     System.out.println("Error reading the file");
   }

   } /// end of main

 } // end of class

Answer 1

What you need is to end the while(sc.hasNext()) while loop because the Scanner sc will always have a next because you are literally saying asking yourself if you got the line from the user then wait for next line with sc.nextLine(); then you are putting it into a string so next time you ask yourself do i have the line the answer is yes,anyways it's a little complicated to get over this issue you need to change the while loop to have a special word that will brake it,so you have to change it from:

  while(sc.hasNext()){
     String line=sc.nextLine();
     if(line.contains("LANTALK"))
     System.out.println(line);
   }

To,for example:

   while(true){
     String line=sc.nextLine();
     if(line.contains("LANTALK"))
     System.out.println(line);
     if(line.contains("END"))
      break;
   }

Also you need to check if the file entered by the user exists and actually add the text from the console to the file,so it would look something like this:

 if(!log.exists())log.createNewFile();
// Connecting to a file with a buffer
   PrintWriter logFile = new PrintWriter(
                          new BufferedWriter(
                           new FileWriter(log.getAbsolutePath())));
   while(true){
     String line=sc.nextLine();
     if(line.contains("LANTALK"))
     System.out.println(line);
     if(line.contains("END"))
      break;
     logFile.println(line);

   }

   logFile.close();

Now all we have to do is print the output to the console when writing it to the logFile,so the while((textLine = infile.readLine()) != null),will now look a little something like this:

  while((textLine = infile.readLine()) != null)
   {
     //System.out.printf("%s\n",textLine);
     outLine = textLine.toUpperCase();
     outFile.println(outLine);
     System.out.println(outLine);
   }// end of while 
   } // end of try

So in the end the hole thing should look a little something like this:

import java.util.*;
import java.io.*;

public class Classname{

   static Scanner sc = new Scanner(System.in);

   public static void main(String args[]) throws IOException, 
   FileNotFoundException {

   String filename;

   // Connecting to a file with a buffer
   PrintWriter outFile = new PrintWriter(
                          new BufferedWriter(
                           new FileWriter("chatOutput.log")));

   // Get the file
   System.out.print("Please enter full name of the file: ");
   filename = sc.next();

   // Assign the name of the text file to a file object
   File log = new File(filename);
   String textLine = null; // Null
   String outLine = "";    // Null

   if(!log.exists())log.createNewFile();
// Connecting to a file with a buffer
   PrintWriter logFile = new PrintWriter(
                          new BufferedWriter(
                           new FileWriter(log.getAbsolutePath())));
   while(true){
     String line=sc.nextLine();
     if(line.contains("LANTALK"))
     System.out.println(line);
     if(line.contains("END"))
      break;
     logFile.println(line);

   }

   logFile.close();

   try{
     // assigns the file to a filereader object..this will throw an error if  the file does not exist or cannot be found
     BufferedReader infile = new BufferedReader(new FileReader(log));

   try
   {
     // read data from a file..this will throw and error if something goes wrong reading (empty or past end of file)
     while((textLine = infile.readLine()) != null)
   {
     //System.out.printf("%s\n",textLine);
     outLine = textLine.toUpperCase();
     outFile.println(outLine);
     System.out.println(outLine);
   }// end of while 
   } // end of try

  finally  // finally blocks get executed even if an exception is thrown 
   {
     infile.close();
     outFile.close();
   }
   }// end of try

 catch (FileNotFoundException nf) // this goes with the first try because it  will throw a FileNotFound exception
   {
     System.out.println("The file \""+log+"\" was not found"); 
   }
 catch (IOException ioex) // this goes with the second try because it will throw an IOexception
   {
     System.out.println("Error reading the file");
   }

   } /// end of main

 } // end of class

If this is not what you are looking for i'm sorry,but i tried to make it do want you described you wanted,i mean it does write the output to the file, and get the output to display in the compiler,here's what the compiler console looks like:

Please enter full name of the file: test.txt
hi
hi
hi
END

HI
HI
HI

I'm sorry if this is not what you wanted but i tried my best,hope it helps.