Java: How to Read a Text File

Reading a plain text file in Java

ASCII is a TEXT file so you would use Readers for reading. Java also supports reading from a binary file using InputStreams. If the files being read are huge then you would want to use a BufferedReader on top of a FileReader to improve read performance.

Go through this article on how to use a Reader

I'd also recommend you download and read this wonderful (yet free) book called Thinking In Java

In Java 7:

new String(Files.readAllBytes(...))

(docs)
or

Files.readAllLines(...)

(docs)

In Java 8:

Files.lines(..).forEach(...)

(docs)

How to read a text file in Java Eclipse?

You are printing the Scanner object, not the File read.
To do that you have to run over the Scanner content, here is an example:

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

public class Main {
    public static void main(String[] args) throws FileNotFoundException {
        System.out.println(System.getProperty("user.dir"));
        File file = new File(System.getProperty("user.dir") + "/src/report.txt");
        Scanner hemp = new Scanner(file);
        while (hemp.hasNextLine()) {
            System.out.println(hemp.nextLine());
        }
    }
}

If you want to read more about the Scanner functions you can see the API docs:

• Scanner.hasNextLine()
• Scanner.nextLine()

Reading and displaying data from a .txt file

BufferedReader in = new BufferedReader(new FileReader("<Filename>"));

Then, you can use in.readLine(); to read a single line at a time. To read until the end, write a while loop as such:

String line;
while((line = in.readLine()) != null)
{
    System.out.println(line);
}
in.close();

How to read text files in java and access those value

It sounds like you want to read from a file? The Scanner class is very good for that.

You will have to format your text document in a different way, which means if you are programmatically writing the file, you need to split the 2 variables somehow. In my opinion, a comma (,) or a colon (:) are the easiest things to choose.

• server_state:running
• health_state:ok
• heappercent:0.2 // Percentages will use floats/decimals
• hoggingthreadcount:10

• stuckthreadcount:1

  public void getProps() {
    String[] cur = new String[2];
    Scanner scanner = new Scanner("C:\Path/To/Your/File.txt");
    while(scanner.hasNextLine()) {
      cur = scanner.nextLine().split(":"); // a colon is simpler.
      if(cur[0].equalsIgnoreCase("server_state")) {
        server_state = cur[1];
      }
      if(cur[0].equalsIgnoreCase("health_state")) {
        health_state = cur[1];
      }
      if(cur[0].equalsIgnoreCase("heappercent")) {
        heappercent = Double.parseDouble(cur[1]);
      }
      if(cur[0].equalsIgnoreCase("hoggingthreadcount")) {
        hoggingthreadcount = Integer.parseInt(cur[1]);
      }
      if(cur[0].equalsIgnoreCase("stuckthreadcount")) {
        stuckthreadcount = Integer.parseInt(cur[1]);
      }
    }
    scanner.close();
  }
  

I hope this solves your problem!

Jarod.

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);
       }
   }
}

read text file in Spring boot

In spring you have to put your file in src/main/resources directory and then you can read it using @Value annotation.

class YourClass {

    @Value("classpath:serviceAccountKey.json")
    private Resource resource;

    @PostConstruct
    public void Initialization() {

        try {
            FirebaseOptions options = new FirebaseOptions.Builder()
                  .setCredentials(GoogleCredentials.fromStream(resource.getInputStream()))
                  .build();

            FirebaseApp.initializeApp(options);
        } catch (Exception e) {
            System.out.println("something went wrong in firebase initialization ...");
            System.out.println(e);
        }

    } 
}

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