Thread: Best Method to Extract Part of a Text File?

I have a text file where I need to search and extract a portion of it (sample file attached). This is a little more complicated than most examples I have seen e.g. using the scanner class. This file is for a microwave antenna containing several sets of data depending on the polarity combination e.g. HH, VV etc..

The search sequence should be as follows:
1. find the line containing the polarity combination
2. find the line containing -180.0 and start the extraction (to an arraylist ?)
3. find the line containing 180.0 and end the extraction

Any guidance in this would be helpful.

OK, I have got this working for the most part, however instead of capturing the -180.0 and 180.0 portions of the first and last lines in the range to the arraylist, it prints zero values for these instead. Has anyone come across this before? The source code and test file are attached.

As requested, here is the code to extract a portion of a text file. It however, on the first and last lines of the extracted text, returns 0.0 instead of -180.0 and 180.0

package test;
 
import java.util.ArrayList;
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.logging.Level;
import java.util.logging.Logger;
 
/**
 *
 * @author gary
 */
public class TEST {
 
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try (Scanner extractpolinfoscanner = new Scanner(new File("/home/gary/NetBeansProjects/TEST/2818B.ADF"))) {
            String polcomb = "H/H";
 
            searchforpolcombloop:
            while(extractpolinfoscanner.hasNextLine()){
                String str = extractpolinfoscanner.findInLine(polcomb);  
                if(str != null)
                {
                    // if polcomb is found, then search for -180.0 and start extracting the lines to an arraylist, searching
                    //for 180.0, then when found skip back to the next row of the spreadsheet
                    String startstr = String.valueOf(-180.0);
                    String endstr = String.valueOf(180.0);
                    ArrayList antpattern = new ArrayList();
                    // search for the line containing -180.0, save it to the arraylist, then skip to the loop that searches for 180.0
                    while(extractpolinfoscanner.hasNextLine()){
                        String startpatt = extractpolinfoscanner.findInLine(startstr);
                        if(startpatt != null){ // if it finds -180.0, add that line to the arraylist
                            antpattern.add(extractpolinfoscanner.nextLine());
                            break;
                        }
                        extractpolinfoscanner.nextLine();
                    }
                    // search for the line containing 180.0, meanwhile saving each line to the arraylist then skip out of the loop
                    while(extractpolinfoscanner.hasNextLine()){
                        String endpatt = extractpolinfoscanner.findInLine(endstr);
                        antpattern.add(extractpolinfoscanner.nextLine());
                        if(endpatt != null){ // if it found 180.0, break out of the search loop 
                            System.out.println("Contents of the antpattern arraylist:"); //this is only for testing
                            for(int j = 0; j < antpattern.size(); j++) {   
                            System.out.println(antpattern.get(j));
                            }
                            break searchforpolcombloop;
                        }
                    }
                }
                extractpolinfoscanner.nextLine();
 
            }
        } 
        catch (FileNotFoundException ex) {
            Logger.getLogger(TEST.class.getName()).log(Level.SEVERE, null, ex);
        }    
    }
 
}

This is the input file:

REVNUM:,NSMA WG16.99.050
REVDAT:,19990520
ANTMAN:,ANDREW CORPORATION
MODNUM:,HP6-71W
PATNUM:,2818B
FEDORN:,NA
DESCR1:,
DESCR2:,
DESCR3:,
DESCR4:,
DESCR5:,
DTDATA:,19911216
LOWFRQ:,7125
HGHFRQ:,8500
GUNITS:,DBI/DBR
LWGAIN:,39.7
MDGAIN:,40.3
HGGAIN:,41.1
AZWIDT:,1.50
ELWIDT:,1.50
ATVSWR:,1.06
FRTOBA:,66.0
ELTILT:,0
PATTYP:,ENVELOPE
NOFREQ:,NA
PATFRE:,NA
NUMCUT:,4
PATCUT:,AZ
POLARI:,H/H
NUPOIN:,41
-180.00,-66.00,
-100.00,-66.00,
-61.72,-46.09,
-55.00,-43.00,
-30.90,-39.98,
-26.43,-38.00,
-15.00,-37.00,
-13.67,-34.03,
-9.75,-33.20,
-5.08,-24.94,
-2.33,-24.94,
-2.33,-19.99,
-2.17,-15.03,
-1.92,-9.91,
-1.75,-7.93,
-1.58,-5.95,
-1.25,-3.96,
-1.00,-2.15,
-0.75,-1.16,
-0.50,-0.33,
0.00,0.00,
0.50,-0.33,
0.75,-1.16,
1.00,-2.15,
1.25,-3.96,
1.58,-5.95,
1.75,-7.93,
1.92,-9.91,
2.17,-15.03,
2.33,-19.99,
2.33,-24.94,
5.08,-24.94,
9.75,-33.20,
13.67,-34.03,
15.00,-37.00,
26.43,-38.00,
30.90,-39.98,
55.00,-43.00,
61.72,-46.09,
100.00,-66.00,
180.00,-66.00,
PATCUT:,AZ
POLARI:,H/V
NUPOIN:,19
-180.00,-72.00,
-100.98,-72.00,
-27.42,-51.21,
-15.00,-47.00,
-11.00,-47.00,
-10.00,-46.00,
-3.42,-46.00,
-2.17,-42.79,
-1.58,-30.00,
0.00,-30.00,
1.58,-30.00,
2.17,-42.79,
3.42,-46.09,
10.25,-46.09,
11.00,-47.00,
15.00,-47.00,
27.42,-51.21,
100.98,-72.00,
180.00,-72.00,
PATCUT:,AZ
POLARI:,V/V
NUPOIN:,45
-180.00,-66.00,
-95.00,-66.00,
-61.72,-52.04,
-37.36,-45.10,
-19.97,-36.01,
-15.00,-33.00,
-12.50,-31.00,
-9.00,-31.00,
-8.00,-28.00,
-7.50,-26.50,
-6.00,-26.50,
-5.00,-25.00,
-3.17,-25.00,
-2.17,-24.94,
-2.17,-19.82,
-2.17,-14.87,
-1.92,-9.91,
-1.67,-6.77,
-1.25,-3.96,
-1.00,-1.98,
-0.83,-0.99,
-0.50,-0.33,
0.00,0.00,
0.50,-0.33,
0.83,-0.99,
1.00,-1.98,
1.25,-3.96,
1.67,-6.77,
1.92,-9.91,
2.17,-14.87,
2.17,-19.82,
2.17,-24.94,
3.17,-25.00,
5.00,-25.00,
6.00,-26.50,
7.50,-26.50,
8.00,-28.00,
9.00,-31.50,
12.50,-31.50,
15.00,-33.00,
19.97,-36.01,
37.36,-45.10,
61.72,-52.04,
95.00,-66.00,
180.00,-66.00,
PATCUT:,AZ
POLARI:,V/H
NUPOIN:,29
-180.00,-72.00,
-101.97,-72.00,
-61.72,-56.00,
-50.00,-56.00,
-45.00,-55.00,
-28.00,-55.00,
-21.96,-50.72,
-15.00,-50.06,
-9.08,-50.06,
-6.92,-46.09,
-3.50,-46.09,
-2.75,-39.98,
-2.00,-39.98,
-1.58,-30.00,
0.00,-30.00,
1.58,-30.00,
2.00,-39.98,
2.75,-39.98,
3.50,-46.09,
6.92,-46.09,
9.08,-50.06,
15.00,-50.06,
21.96,-50.72,
28.00,-55.00,
45.00,-55.00,
50.00,-56.00,
61.72,-56.00,
101.97,-72.00,
180.00,-72.00,
ENDFIL:,EOF

This is the output:

Contents of the antpattern arraylist:
0,-66.00,
-100.00,-66.00,
-61.72,-46.09,
-55.00,-43.00,
-30.90,-39.98,
-26.43,-38.00,
-15.00,-37.00,
-13.67,-34.03,
-9.75,-33.20,
-5.08,-24.94,
-2.33,-24.94,
-2.33,-19.99,
-2.17,-15.03,
-1.92,-9.91,
-1.75,-7.93,
-1.58,-5.95,
-1.25,-3.96,
-1.00,-2.15,
-0.75,-1.16,
-0.50,-0.33,
0.00,0.00,
0.50,-0.33,
0.75,-1.16,
1.00,-2.15,
1.25,-3.96,
1.58,-5.95,
1.75,-7.93,
1.92,-9.91,
2.17,-15.03,
2.33,-19.99,
2.33,-24.94,
5.08,-24.94,
9.75,-33.20,
13.67,-34.03,
15.00,-37.00,
26.43,-38.00,
30.90,-39.98,
55.00,-43.00,
61.72,-46.09,
100.00,-66.00,
0,-66.00,

The first line of the arraylist should be -180.0,-66.00, and the last line should be 180.0,-66.00, to agree with the information extracted from the input file.

At this point I don't want to print anything. There will be further code to process/use the information in the arraylist.

I thought it would be redundant to save a portion of the input file rather than to just create a temporary arraylist and use it from that point.

Thanks, I'll have to dig in further.

Your first input file doesn't have the same as the input data you have given.

If your conditions are as simple as you given in the original post, i think you are over-complicating the algorithm. I know we aren't encouraged to paste complete code but
how about something like this:

package main;
 
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
 
public class ParseTest {
 
	public static void main(String[] args) {
 
		// flag to store
		boolean  isToBeSaved = false;	
		//Storage
		  ArrayList<String> lines = new ArrayList<String>();
		//keys 
		  String startStr = "-180.0";
		  String endStr = "180.0";
		//Data file
		String filePath = "C:\\Temp\\data.txt";
 
		System.out.println("START OF READ LINES");
 
		Scanner in;
		try {
			in = new Scanner(new File(filePath));
 
			while ( in.hasNextLine() ) { // go trough all the lines in the data file
				String line = in.nextLine();
				System.out.println("\t" + line); //for debugging
				if ( isToBeSaved ) { // is the line between start and end strings ( the -180 and 180 )
					lines.add(line); // save the data
					if ( line.contains(endStr)) 
						isToBeSaved = false;
				} else { 
					if ( line.contains(startStr)) { 
						isToBeSaved = true;
						lines.add(line);
					}
				}
			}
			in.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
 
		System.out.println("END OF READ LINES\n\n");
 
 
		printStoredLines(lines);
 
	}
 
        //method to print out the stored data.
	public static void printStoredLines(ArrayList<String> lines) {
		System.out.println("START OF THE STORED LINES");
		for ( String storedLine : lines ) 
			System.out.println(storedLine);
		System.out.println("END OF THE STORED LINES");		
	}
 
}