stop looping if method read next line empty

Question

i do not know if the title is correct. what i want to ask is how to stop looping if next line from method is empty. i have 2 method:

public static void main(String[] args) throws Exception {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    rrr thisObj = new rrr();
    String command = br.readLine();
      while ((command = br.readLine())!=null) {
         int b=0;
         thisObj.perintah(b,command);
      }
}  

public void perintah(Integer indek, String PesanSumber)
   {
       String Pesan = PesanSumber.trim();
       int panjang = Pesan.length();
       if (panjang >=3)
       {
           if (Pesan.toLowerCase().trim().substring(0, 3).equals("log") )
            {
              System.out.println("bla bla bla");
            }
           else if (Pesan.toLowerCase().trim().substring(0, 4).equals("move"))
            { 
              System.out.println("bla bla bla");
            }
           else if (Pesan.toLowerCase().trim().substring(0, 4).equals("move"))
            { 
              System.out.println("bla bla bla");
            }
       }
    }

the problem is if i run it's not stop even next line is empty.

@zakinster if he wants to stop on the first empty line (before EOF) he will need to add `&& !command.isEmpty()` or possibly `&& !command.trim().isEmpty()` — Alowaniak, Oct 09 '13 at 12:42

zakinster · Accepted Answer · 2013-10-09T12:43:24.940

3

 String command = br.readLine();
 while ((command = br.readLine())!=null) {

First, you're missing the first line by calling readLine() before the loop. Secondly, you can add a second condition to check if the line is empty when it's not null :

 String command;
 while ((command = br.readLine())!=null && !command.isEmpty()) {

Now, it should stops where a line is empty or where there is no new line in the stream.

edited Oct 09 '13 at 12:43

answered Oct 09 '13 at 12:33

zakinster

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2

From [javadocs](http://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html#readLine%28%29): `BufferedReader.readLine()` return null when EOF is reached. He/she will get a NPE in this case. – Mauren Oct 09 '13 at 12:35

score 1 · Answer 2 · answered Oct 09 '13 at 12:42

1

You're trying to initialize the string twice, reading an empty line, so just change

String command = br.readLine();

to

String command;

answered Oct 09 '13 at 12:42

Troubleshoot

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I didn't even noticed ;) – Julien Oct 09 '13 at 12:43

Ruchira Gayan Ranaweera · Answer 3 · 2013-10-09T12:41:55.557

0

you can try following. Now it will stop.

 String command;
  while ((command = br.readLine())!=null) {
     int b=0;
     thisObj.perintah(b,command);
  }

In your code

  String command = br.readLine(); // you read empty line
  while ((command = br.readLine())!=null) { // But command will override by next line
     int b=0;
     thisObj.perintah(b,command);
  }

edited Oct 09 '13 at 12:41

answered Oct 09 '13 at 12:36

Ruchira Gayan Ranaweera

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score 0 · Answer 4 · edited May 23 '17 at 11:50

0

With a Scanner, you can also use .hasNext() .next() methods which is quite a classical way of doing things. Example here : BufferedReader pointer

edited May 23 '17 at 11:50

Community

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1

answered Oct 09 '13 at 12:39

Julien

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score 0 · Answer 5 · answered Oct 09 '13 at 13:01

0

I was just going through your code, String command = br.readLine(); should be replaced with String command = ""; otherwise your first input will be missed. And to answer your question, System.in does not returns null, so you must check for empty string as String command;// br.readLine(); while (!(command = br.readLine()).isEmpty()) { int b = 0; thisObj.perintah(b, command); }

This should work fine.

answered Oct 09 '13 at 13:01

codingenious

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not good,my indek still zero after if im input move for time. – pound Pound Oct 09 '13 at 13:14
catatLog.put(indek,Nilai); i have that code in move condition – pound Pound Oct 09 '13 at 13:15
I am not clear about what you asking, can you please explain? – codingenious Oct 09 '13 at 15:12

stop looping if method read next line empty

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