Reading a .Txt File Using Scanner Class in Java

Reading a .txt file using Scanner class in Java

You have to put file extension here

File file = new File("10_Random.txt");

Reading char with scanner from txt file and adding to a 2d array

Scanner.next() always returns a String. Please check https://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html for more information. Before performing any operation on scan.next() e.g. scan.next().charAt(0), you should check if (scan.hasNext()) condition.

Reading in a .txt file in Java

Here is a full running answer if you are still interested...

For input file:

 node1   node2
 node1   node3
 node2   node3
 node3   node5
 node2   node3 <<< repeating
 node2   node6
 node1   node3 <<< repeating

The filtered output:

 node1   node2 
 node1   node3 
 node2   node3 
 node3   node5 
 node2   node6 

SHORT ANSWER:
Use HashMap<String, String> and

check repeating nodes with
x_nodes.containsKey(x_key) && x_nodes.containsValue(x_value)

DETAILED ANSWER:
Copy & paste the following source:

public static char       q_TEXT_SEPARATOR            = '|';
public static int        q_MAX_TEXT_LINE_NBR         = 1000;
public static char       q_ALT_ENTER                 = '\n';
public static String     q_CUSTOM_COMMENT_CHAR       = "*";
public static String     q_CUSTOM_SPLIT_CHAR         = " ";

public static HashMap<String, String> w_nodes = new HashMap<String, String>();

public static boolean empty_line(String input) {
    boolean w_bos_bilgi = (input == null || input.equals("") || input.trim().equals(""));
    return  w_bos_bilgi;
}

public static String[] custom_split(String s) {
    return custom_split(s, q_TEXT_SEPARATOR);
}
public static String[] custom_split(String s, char   q_TEXT_SEPARATOR) {
    String[] p = new String[q_MAX_TEXT_LINE_NBR];
    for (int i = 0; i < q_MAX_TEXT_LINE_NBR; i++) {
        p[i] = "";
    }

    int totlen = s.length();
    int i = 0;
    int k = 0;
    boolean finish = false;
    while (!finish) {
        if ((k >= totlen) || (i >= q_MAX_TEXT_LINE_NBR)) {
            finish = true;
        } else {
            String w_tx = "";
            boolean finish2 = false;
            while (!finish2) {
                char c = s.charAt(k);
                if ((  c      ==      q_TEXT_SEPARATOR)  || (k > totlen) || (i == q_MAX_TEXT_LINE_NBR)) {
                    finish2 = true;
                } else {
                    if (c != q_ALT_ENTER) {
                        w_tx = w_tx + c;
                    }
                    k = k + 1;
                }
            }
            if (!empty_line(w_tx)) {
                p[i] = w_tx;
                i++;
            }
            k++;
        }
    }

    return p;
}

public static boolean existing(HashMap<String, String> x_nodes, String x_key, String x_value) {
    if ( x_nodes.containsKey(x_key) && x_nodes.containsValue(x_value) ) {return false;}
    else                                                                {return true;}
}

public static void import_nodes() {
   String q_NODES_FILENAME = "C://...//interactions.txt";

   BufferedReader q_NODES_in = null;
   try {
        q_NODES_in           = new BufferedReader(new FileReader(q_NODES_FILENAME));
   } catch (Exception e) {
        System.out.println("> WARNING : Nodes file not found !");
        return;
   }

   String w_file_str = "", w_line = "";
   while ( q_NODES_in != null && w_line != null ) {
       try {
         w_line        = q_NODES_in.readLine();
         if ( empty_line(w_line) ) {continue;}
         if ( w_line.startsWith(q_CUSTOM_COMMENT_CHAR)) {continue;}

         if  ( w_line == null || w_line.equals("null") ) {
              throw new IOException();
         }

         w_file_str   += w_line.replace(q_TEXT_SEPARATOR + "", "") + q_TEXT_SEPARATOR;
       } catch (Exception e) {
           break;
       }
   }
   try {q_NODES_in.close();} catch (Exception e) {}

   if ( empty_line(w_file_str) ) {
          System.out.println("> WARNING : Nodes file empty !");
          return;
   }

   String p[] = custom_split(w_file_str);
   for (int i = 0; i < p.length && !empty_line(p[i]); i++) {
       String w_key   = "";
       String w_node = (p[i] + " ");
       int    w_separator = w_node.indexOf(q_CUSTOM_SPLIT_CHAR);
       if   ( w_separator < 0 ) {continue;}
       else                 {w_key   = w_node.substring(0, w_separator);
                             w_node = w_node.substring(w_separator + 1);}

       if ( p[i].trim().toUpperCase().startsWith(q_CUSTOM_COMMENT_CHAR)) {continue;}                                                                                                                                                                                                                                                                                                     //UPD 2012/10/08

       if ( existing(w_nodes, w_key, w_node)      ) {
            w_nodes.put(w_key, w_node);
            System.out.println(w_key + " " + w_node);
       }
   }
}

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