External references for file writer:
https://www.programiz.com/java-programming/examples/append-text-existing-file

Current Directory (of active program):
https://www.programiz.com/java-programming/examples/current-working-directory

File Writer:
	   public void writeRecord(String pFilePath, String pRecordToWrite) throws IOException {
   
		   System.out.println("Write Info: " + pRecordToWrite + " append string to file: - " + pFilePath);
	   
		   File file = new File(pFilePath); // appendmode
		   FileWriter fr = new FileWriter(file, true);
		   fr.write(pRecordToWrite + "\r\n");
		   fr.close();
	   }	
	   =====================================================
	   Buffered File Reader:
public class FileBufferedReader {  
    public static void main(String args[])throws Exception {    
    	//ArrayList<String> arrayList = new ArrayList<String>();
        String path = "D:\\DeleteFilesToTest\\sheetMusicToFilter.txt";
 
        try (BufferedReader br
             = new BufferedReader(new FileReader(path))) {
 
            String line;
            int i = 0;
            // It holds true till there is content in file
            while ((line = br.readLine()) != null) {
            	//put into the ArrayList list:
            	//arrayList.add(str);
                // Printing the file data
            	i++;
                System.out.println(i + ". " +line);
            }
        }
 
        // Catch block to handle the exceptions
        catch (IOException e) {
 
            // Display pop up message if exceptionn occurs
            System.out.println(
                "Error while reading a file.");
        }
        //return arrayList;
    }
}
	   
==================================
Read File records into ArrayList:
public class ReadFileToTest {
	
	    public ArrayList<String> readBufferedFile(String pReadFilePath)  {
	 
	        // Declaring a string and initializing it with
	        // path of file present on the system
	    	ArrayList<String> arrayList = new ArrayList<String>();
	        String path = pReadFilePath;
	 
	        // Try block to check for exceptions
	        try (BufferedReader br
	             = new BufferedReader(new FileReader(path))) {
	 
	            // Declaring a new string
	            String str;
	 
	            // It holds true till there is content in file
	            while ((str = br.readLine()) != null) {
	            	//put into a list:
	            	arrayList.add(str);
	                // Printing the file data
	                System.out.println(str);
	            }
	        }
	 
	        // Catch block to handle the exceptions
	        catch (IOException e) {
	 
	            // Display message if exceptionn occurs
	            System.out.println(
	                "Error while reading a file.");
	        }
	        return arrayList;
	    }
==================================
	 
File Finder Dialog:
	public void getFilePath() {
		JFileChooser fileChooser = new JFileChooser();
		int option = fileChooser.showOpenDialog((Frame) null);
        		if(option == JFileChooser.APPROVE_OPTION){
           		File file = fileChooser.getSelectedFile();
           		txtFileToTest.setText(file.getAbsolutePath());
        		}else{
        			txtFileToTest.setText("Save command canceled");
        		}
	}

==================================
Directory Finder Dialog:	
	public void getDirectory() {
		LocalDateTime myDateObj = LocalDateTime.now();
		DateTimeFormatter myFormatObj = DateTimeFormatter.ofPattern("yyyy-MM-dd-HH-mm-ss");
		String formattedDate = myDateObj.format(myFormatObj);
		System.out.println(formattedDate);
	       	JFileChooser fileChooser = new JFileChooser();
           		fileChooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
           		int option = fileChooser.showOpenDialog((Frame) null);
           		if(option == JFileChooser.APPROVE_OPTION){
              		File file = fileChooser.getSelectedFile();
             		 txtSaveResultsToDirectoryChoice.setText(file.getAbsolutePath() + "\\FilteredResults-" + formattedDate + ".txt");
           		}else{
        	   		txtSaveResultsToDirectoryChoice.setText("Open Folder command canceled");
           		}
	}
===============================
========================================

public class BufferedInputFile {
// Throw exceptions to console:
public static String
read(String filename) throws IOException {
// Reading input by lines: BufferedReader in = new BufferedReader(
new FileReader(filename));
String s;
StringBuilder sb = new StringBuilder(); while((s = in.readLine())!= null)
sb.append(s + "\n");
in.close();
return sb.toString();
}
public static void main(String[] args) throws IOException {
System.out.print(read("BufferedInputFile.java"));
}
} /* (Execute to see output) *///:~

=============================================

public class FileOutputShortcut {
static String file = "FileOutputShortcut.out"; public static void main(String[] args)
throws IOException {
BufferedReader in = new BufferedReader(
new StringReader(
BufferedInputFile.read("FileOutputShortcut.java"))); // Here’s the shortcut:
PrintWriter out = new PrintWriter(file);
int lineCount = 1;
String s;
while((s = in.readLine()) != null )
out.println(lineCount++ + ": " + s);
out.close();
// Show the stored file: System.out.println(BufferedInputFile.read(file));
}
} /* (Execute to see output) *///:~

===============================================
========================================
Using BufferedReader:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ReadFileLineByLineUsingBufferedReader {

	public static void main(String[] args) {
		BufferedReader reader;

		try {
			reader = new BufferedReader(new FileReader("sample.txt"));
			String line = reader.readLine();

			while (line != null) {
				System.out.println(line);
				// read next line
				line = reader.readLine();
			}

			reader.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

=============================================
Using Files:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class ReadFileLineByLineUsingFiles {

	public static void main(String[] args) {
		try {
			List<String> allLines = Files.readAllLines(Paths.get("sample.txt"));

			for (String line : allLines) {
				System.out.println(line);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}