import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.PrintWriter; import java.util.Scanner; public class Concat {

public boolean accept(File file) {
    //if the file extension is .txt or .java return true, else false
    if (file.getName().endsWith(".txt")||file.getName().endsWith(".java")) {
        return true;
    }
    return false;
}

public void copy(PrintWriter pw, String inputFile)
{
    File f = new File(inputFile);
    if(accept(f)==true){

        try {
            Scanner scan = new Scanner(f);
            pw= new PrintWriter(new FileOutputStream("Stuff.txt"));
            while (scan.hasNextLine())
            {
                String s = scan.nextLine();
                pw.println(s);
            }
            scan.close();
        } catch (FileNotFoundException e) {
            System.out.println(" Error: "+e + " "+ inputFile);
        }
    }else{

        System.out.println("File name must be a TEXT Or JAVA type");

    }
}

// The routine will throw a RuntimeException if the inputFile name does 
// note end with .java or .txt

// This routine will also throw a RuntimeException if any problem occurs in 
// opening the inputFile

// The copy routine copies the contents of the inputFile into the PrintWriter


public void concat(String outFile, String[] inputFiles)
{
    try {
        PrintWriter writer = new PrintWriter(outFile);
        for(int i=0;i<inputFiles.length;i++){
            String source=inputFiles[i];
            copy(writer,source);
        }

    } catch (IOException e) 
    {
        System.err.println(e);
        System.exit(1);
    }

    // Fill in details.
    // The routine will call copy to do a copy of a single file
    // This routine will also create an open PrintWriter for the outFile
    // If any problem occurs, a RuntimeException should be thrown with 
    // appropriate error information
}


public static void main(String[] args) {
    if (args == null || args.length < 2)
    {
        System.out.println("Concat needs at least 2 filenames");
        return;
    }
    try
    {

        String[] inputFiles = new String[args.length-1];
        for (int i=0; i < inputFiles.length; i++)
            inputFiles[i] = args[i+1];
        Concat c = new Concat();
        c.concat(args[0], inputFiles);
    }
    catch (RuntimeException e)
    {
        // Possible errors:
        // An input file that doesn't end with .java or .txt
        // An input file that doesn't open properly.
        // Trouble creating the output file

        System.out.println(" Error in Concat:"+e);
    }
}

}