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Nacho Zve De La Torre
Asked: 2020-10-20 04:57:09 +0800 CST 2020-10-20 04:57:09 +0800 CST

How can I move X characters to the right from a String in Java?

  • 772

The following program reads a txt file line by line:

BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(origin),"ISO-8859-1"));

                String strLine;
                while ((strLine = br.readLine()) != null)   {
                    if(strLine.contains("Fecha de Emision: ")){
                        String date = strLine.substring(84,93);
                        String[] parts = date.split("/");
                        try{
                            int day = Integer.parseInt(parts[0]);
                            if(day < 10){
                                SimpleDateFormat format = new SimpleDateFormat("MM/dd/YYYY");
                                String dateString = format.format(new Date(date));
                                String newDate = strLine.replace(date, dateString);
                                writer.write(newDate+"\n");
                            } else{
                            writer.write(strLine+"\n");
                            }
                        } catch(NumberFormatException nfe){
                            System.out.println("Problema al parsear el día de la fecha");
                            return;
                        }
                    } else{
                        writer.write(strLine+"\n");
                      }
                }
                br.close();

If in the line you are reading you find the String "Issuance Date" what should come next is the date itself (EXAMPLE: 12/06/2018). I am assuming that the date is between positions 84 and 93

String date = strLine.substring(84,93);

But it's not always like this.

What is fixed is that the date always starts two spaces after the String "Issuance Date".

Ask:

How do I tell my program to do that? That is, move two characters to the right from "Issue Date" to be able to later validate the date format and other things that I have already done !!!

From already thank you very much :)

java

2 Answers

  1. Best Answer

    With String.indexOf() you should be able to get the position of the word you indicate, and since it returns -1 if not found, you can replace the contains.
    To get something like this:

    String toFind = "Fecha de Emision: ";
int position = strLine.indexOf(toFind);
if(position >= 0){
    //para cortar el Date a la posición se le suma el largo del string +1, hasta la posición + el largo del string +1 +10 que es el largo de la fecha.
    String date = strLine.substring(position+toFind.length()+1, position+toFind.length()+11);
    String[] parts = date.split("/");
    try{
        int day = Integer.parseInt(parts[0]);
        System.out.println("day "+day);
        if(day < 10){
            SimpleDateFormat format = new SimpleDateFormat("MM/dd/YYYY");
            String dateString = format.format(new Date(date));
            String newDate = strLine.replace(date, dateString);
            writer.write(newDate+"\n");
        } else{
            writer.write(strLine+"\n");
        }
    } catch(NumberFormatException nfe){
        System.out.println("Problema al parsear el día de la fecha");
        return;
    }
} else{
    writer.write(strLine+"\n");
}

    Another way to achieve it would be with Regex , but what I indicate should help you if it always comes like this.

    • 2

  2. You search for the string, position yourself behind it and read what you need:

    public class Main {
    static private String LABEL = "Fecha de emisión: ";
    static private int DATE_LENGTH = 10; // DD/MM/YYYY

    public static void main(String[] args) {
        String s = "En un lugar de la Mancha.... Fecha de emisión: 22/11/2018";

        System.out.println(s.indexOf(LABEL)); // 29

        int index = s.indexOf(LABEL) + LABEL.length();
        System.out.println(s.substring(index, index + DATE_LENGTH));
    }
}

    Try it online!

    • 1