如何使用Scanner类打印纯文本文件？

Question

I'm attempting to create a Scanner Class which is supposed to output a plain text file which contains the following information;

PersonName, Address, City, Phone_Number, PersonName, Address, City, Phone_Number, PersonName, Address, City, Phone_Number, PersonName, Address, City, Phone_Number,

My Delimiter is the commas.

Each set of data has to be output in the form of a Binary Tree. With the Name as the rootnode firstly, then the address as the rootnode, then the city as rootnode and so on.

This is my Java file that i've created and it simply outputs "usage: java Scanner_Two telephone.txt " + "file location" everytime with no tree underneath. Can anyone show me where i've gone wrong. Ive created an Entry class, BinaryTreeNode class and Binary Tree class aswell.

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

public class Scanner_Two
{

     private static void readFile(String TreeName)
     {

       try {
      // Scanner input = new Scanner (new File("telephone.txt")).useDelimiter("\\s*,\\s*");
         Scanner scanned = new Scanner(new File(TreeName));

         scanned.useDelimiter
            (System.getProperty("line.separator"));

         while (scanned.hasNext())
         {
           parseLine(scanned.next());
         }

         scanned.close();
       } catch (FileNotFoundException e) {
         e.printStackTrace();
       }
     }

private static void parseLine(String line)
{
       Scanner lineScanner = new Scanner(line);
       lineScanner.useDelimiter("\\s*,\\s*");

       String rootnode = lineScanner.next();
       String bone = lineScanner.next();
       String btwo = lineScanner.next();
       String bthree = lineScanner.next();

       System.out.println("Name: " + rootnode + " Address: " + bone + ", City: " + btwo + ", Telephone Number: " + bthree);
}

public static void main(String[] args)
{
       if(args.length != 1)
       {

         System.out.println("usage: java Scanner_Two Person.txt " + "file location");
         System.exit(0);

       }

       readFile(args[0]);
}

}

Answer 1

If you are using

if(args.length != 1)
 {           
     System.out.println("usage: java Scanner_Two Person.txt " + "file location");    
     System.exit(0);    
 }    

and you get this message actually printed out, it means that you either have less than 1 parameter or more than one parameter. You should check this.

Answer 2

The issue that you are describing is not an issue with the Scanner class, as you had indicated in your title, but in fact in your handling of arguments. In the following code, (located in your main method) we can see that your program fails before it even hits a Scanner declaration:

if(args.length != 1) {
System.out.println("usage: java Scanner_Two Person.txt " + "file location");
System.exit(0);
}

Since this code is executing, we know that args comes into the main method with either 0 or more than 1 element. I'm going to take a wild swing and guess that you're a newbie, in which case you should really be looking into how to use command line arguments . Typically command line arguments are only used if you're executing through some command line environment (such as terminal or command prompt). If you're using an IDE, entering such parameters can be done although it is IDE specific.

If you tell us specifically how you are executing the code, and, if you do it through the command-line, the specific command you use, I could provide a more detailed answer.

Even easier than learning about command line environments, and more convenient for repeated testing, would be using a hardcoded main method:

public static void main(String[] args) {
readFile("C:\\[filepath]\\Person.txt");
}