Java code not reading arguments

Question

For a class that I have, I have to take arguments, which will be files with different urls on each line, and run through the lines to count the amount of times each url has different schemes and different domains. If there is no argument, than I have to scan in directly what is typed. I have gotten the following code, which includes everything except the printlns at the end.

import java.util.Scanner;
public class P1 {
  public static void main(String[] args){
    int fileLinesCt=0, totalLinesCt=0;
    int httpCt=0, httpsCt=0, ftpCt=0, otherSchemeCt=0;
    int eduCt=0, orgCt=0, comCt=0, otherDomainCt=0;
    String url, scheme, schemeSP, domain = null;
    Scanner scan = null;

    if(!args.equals(null)){
        for (int j=0; j<args.length; j++){
            scan = new Scanner(args[j]);
            fileLinesCt = 0;
            while (!"end".equals(scan.nextLine())){
                url = scan.nextLine();
                String[] parts = url.split("//://");
                scheme = parts[0];
                schemeSP = parts[1];
                if ("http".equals(scheme))
                    httpCt++;
                if ("https".equals(scheme))
                    httpsCt++;
                if ("ftp".equals(scheme))
                    ftpCt++;
                else otherSchemeCt++;
            for (int i=0; i<schemeSP.length(); i++){
                if (schemeSP.charAt(j) == '.')
                    domain = schemeSP.substring(j,'/');
                if (schemeSP.charAt(j) == '/')
                    break;
            }
            if ("edu".equals(domain))
                eduCt++;
            if ("org".equals(domain))
                orgCt++;
            if ("com".equals(domain))
                comCt++;
            else otherDomainCt++;
            fileLinesCt++;
            totalLinesCt++;
            if (fileLinesCt == 1)
                System.out.println(">> Got " + fileLinesCt + " line from " + scan);
            else System.out.println(">> Got " + fileLinesCt + " lines from " + scan);
            }
        }
    }
    else {
        Scanner scanner = new Scanner(System.in);
        fileLinesCt = 0;
        while (!scanner.next().equals("end")){
            url = scanner.next();
            String[] parts = url.split("//://");
            scheme = parts[0];
            schemeSP = parts[1];
            if ("http".equals(scheme))
                httpCt++;
            if ("https".equals(scheme))
                httpsCt++;
            if ("ftp".equals(scheme))
                ftpCt++;
            else otherSchemeCt++;
            for (int j=0; j<schemeSP.length(); j++){
                if (schemeSP.charAt(j) == '.')
                    domain = schemeSP.substring(j,'/');
                if (schemeSP.charAt(j) == '/')
                    break;
            }
            if ("edu".equals(domain))
                eduCt++;
            if ("org".equals(domain))
                orgCt++;
            if ("com".equals(domain))
                comCt++;
            else otherDomainCt++;
            fileLinesCt++;
            totalLinesCt++;
            if (fileLinesCt == 1)
                System.out.println(">> Got " + fileLinesCt + " line from " + scan);
            else System.out.println(">> Got " + fileLinesCt + " lines from " + scan);
        }
    }

When running the code, I get an error that says

"Program failed when listing file(s) on command line.
Exception in thread "main" java.util.NoSuchElementException: No line found" This occurs at line 15 when it tries to scan the next line.

What am I doing wrong that would stop it from scanning the next line?

The statement if(!args.equals(null)) always return true. Are you sure that's you want? — Omar Mainegra
– Omar Mainegra, Commented Sep 18, 2013 at 19:42

M Abbas · Accepted Answer · 2013-09-18 19:42:25Z

2

Thats because you are calling scan.nextLine twice

while (!"end".equals(scan.nextLine())){
    url = scan.nextLine();

You should do this instead:

while ( !("end".equals((url = scan.nextLine()))) ) {
    ...
}

answered Sep 18, 2013 at 19:42

M Abbas

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1 Comment

user2780232 Over a year ago

I tried this and it seems that this didn't fix the issue. With this changed do you have any idea why this may still be happening?

sheltem · Accepted Answer · 2013-09-18 19:41:39Z

0

You are skipping a line at the start of each while-run.

scan.nextLine()

That advances the scanner past the line that is being returned, so

  while (!"end".equals(scan.nextLine())){
            url = scan.nextLine();

means url contains the second line. Which also means that it might skip over the end-condition, leading to it trying to read a line that doesn't exist.

scan.hasNextLine() is the way to check for the end of the file that you are looking for.

answered Sep 18, 2013 at 19:41

sheltem

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Marckvdv · Accepted Answer · 2013-09-18 19:45:33Z

0

args is never null (I believe), try args.length != 0 instead.

answered Sep 18, 2013 at 19:45

Marckvdv

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Math · Accepted Answer · 2013-09-18 19:49:10Z

0

The statement below

if(!args.equals(null)){

Could be switched by

if(args.length > 0){

Once using .equals in the String array args doesn't say whether is contains elements or not.

edited Sep 18, 2013 at 19:49

answered Sep 18, 2013 at 19:42

Math

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