Java search text file for string and replace or remove a character within the string

ProgrammerLarry :

I'm working with a large text file that has thousands of lines of text that contain some information. Sometimes the software will randomly add a character in place which will fail our upload. I'm trying to create a program that finds a string that is hard coded and then searches within the line and replaces or removes the invalided character. Here is some of the contents of the text file.

    MTR17000386001000000000000000RA              124359      
    00010000004000000040000000 000NN  NNE 000                       N    
    RDG17000386 
    KWHL000000000R00000100000059534000405162019075929N000400000010N8486     
    000010500R 00000010010000059226           
    RFF1700038652126007      ERT      
    0000000952.0062500070014051620190759290005953476Type 7  0000N    6
    MTR17000386001000000000000000RA              114818      
    00010000005000000050000000 000NN  NNE 000                       N    
    RDG17000386 
    DMDL000000000R000001000.0072666035305162019112344N000100000010N8486     
    005180500R 00000010010000072666           
    RFF1700038611861733      ERT      
    0000000952.0062500070000051620191123440007266680Type 7  0000N    6

On the line of RDG17000386 DMD you can see that there is a period. The period is not supposed to be there and needs to be replaced or removed from the file.

In my current code I"m searching each line that start with "RDG" and it works find, but I want to limit the search with only the lines that include "DMD" within the line and I've tried changing the RDG to DMD, which didn't work because the line doesn't start with DMD. I'm not entirely sure how to remove or replace the period from the file. Here is what my code looks like so far.

 import java.io.*;

 public class ReadLineAndReplace {

public static void main(String[] args) throws IOException {

    BufferedReader br = new BufferedReader(new FileReader("FilePath"));
    StringBuilder sb = new StringBuilder();
    String line = "";

    while ((line = br.readLine()) != null) {

        if (line.startsWith("RDG")) {
        //assuming the replace would be inserted here   
            System.out.println(line);       
        }
    }
}
}

Joakim Danielson :

Use. matches() with a regular expression

line.matches("^RDG.*DMD.*")

to replace the dot with a zero

if (line.matches("^RDG.*DMD.*")) {
    line = line.replace('.', '0')
}