How to get index value while reading from a file in java

Question

I wrote a piece of code to read value from a file ,

public class Test { 
    public static void main(String[] args) throws Exception { 
    // pass the path to the file as a parameter 
        FileReader fr = new FileReader("/home/workspace_ag7_tmv/Message Router/environments/wb/conf/subscriber_content_restriction.conf"); 
        int i; 
        while ((i=fr.read()) != -1) {
            System.out.print((char) i); 
        } 
    }
}

In my file I passed these value : PRE|00000000110000200000049U POS|10000000110000200000049U

I am able to get these values using above piece of code, Now I want to fetch 4th index value. Can you please help me how to do same ?

can you share , file screenshot then we can get idea about line sequence — Dulaj Kulathunga
– Dulaj Kulathunga, Commented Oct 4, 2019 at 5:49
PRE|00000000110000200000049U POS|10000000110000200000049U This is the file, I need to get value after PRE or POS i.e here, after PRE we have 0 value — Ritika
– Ritika, Commented Oct 4, 2019 at 5:59
If i recognize a pattern you want to eventually get the | position? or you want exactly the 4th char in index which may or may not be the | character? — ckinfos
– ckinfos, Commented Oct 4, 2019 at 6:02
I want the index of value after '|' position.Here it is 0 for PRE and 1 for POS — Ritika
– Ritika, Commented Oct 4, 2019 at 6:05

rambis · Accepted Answer · 2019-10-04 06:37:33Z

1

You could add the chars to an ArrayList and then get the element at the 4th index.

int i;
List<Character> charList = new ArrayList<>();    

while ((i=fr.read()) != -1) 
  charList.add((char) i);
  System.out.print((char) i); 
  }

// to get char at index 4
char a = charList.get(4);

After reading your other questions: If you want to get the index of the value that comes after '|' then you can convert the List to a String and get the indexOf '|' and add an 1 to that index.

Something like:

int i;
List<Character> charList = new ArrayList<>();    

while ((i=fr.read()) != -1) 
  charList.add((char) i);
  System.out.print((char) i); 
  }

      String str= charList.stream()             
                        .map(String::valueOf)   
                        .collect(Collectors.joining()); 
int firstPos = str.indexOf('|');
System.out.println(str.charAt(firstPos+1));

int secondPos = str.indexOf('|', firstPos+1);
System.out.println(str.charAt(secondPos+1));

edited Oct 4, 2019 at 6:37

answered Oct 4, 2019 at 5:49

rambis

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2 Comments

Ritika Over a year ago

I tried but I am getting '?' while running above piece of code

Dulaj Kulathunga Over a year ago

try to archive what he is asking

ckinfos · Accepted Answer · 2019-10-04 06:35:26Z

0

/***********************************
    * a bit of ugly code               *
    * you read all lines in a list
    * you cycle the list and tokenizeit*
    * you get the PRE digit char in i  *
    * and the POS digit in i2          * 
    ***********************************/
    public class GetAllLines {
        StringTokenizer sToken;
        String s;
        public static void main(String[] args) {
            try {
                List<String> lines = Files.readAllLines(Paths.get("/home/workspace_ag7_tmv/Message Router/environments/wb/conf/subscriber_content_restriction.conf"));
                for (String line : Lines) {
                    sToken = new StringTokenizer(line, "|");
                    while (sToken.hasMoreElements()) {
                        //you can get after PRE 1st digit
                        s=sToken.nextElement().nextElement().toString();//the 1st getElementgets the PRE the 2nd gets all string up to POS
                        int i = Integer.parseInt(s.getSymbol(0).charAt(0)); //you get the next to PRE
                        s=sToken.nextElement().toString();//the 3rd getElement gets all string after POS
                        int i2 = Integer.parseInt(s.getSymbol(0).charAt(0)); //you get the next digit after POS
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

answered Oct 4, 2019 at 6:35

ckinfos

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1 Comment

ckinfos Over a year ago

You could also stringtokenize with PRE and then POS too. Depends on what you want to do later in code with the line string. hope i gave you some help. You could even "for" the linestring upto 4 or 30 times empty and get the value there. many options on these.

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