Java : Read whole file to...

// https://howtodoinjava.com/java/io/java-read-file-to-string-examples/
// https://stackoverflow.com/questions/19486077/java-fastest-way-to-read-through-text-file-with-2-million-lines
// http://net-informations.com/q/faq/memory.html
// http://www.java2s.com/Tutorials/Java/java.nio.file/Files/Java_Tutorial_Files.htm

import java.io.*;
import java.nio.file.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.*;
//import org.apache.commons.io.*;

public class m {
    public static void main(String[] args) throws InterruptedException {
        try {
            byte[] bytes = Files.readAllBytes(Paths.get(args[0])); //  // a "legjobb" memóriafoglalás: 164 MB -> 340 MB
            //String str = new String(bytes, StandardCharsets.UTF_8);
            //List<String> lines = Files.readAllLines(Paths.get(args[0]),Charset.forName("ISO-8859-2")); // túlzott memóriafoglalás: 164 MB -> 775 MB
            //String str1 = new String ( Files.readAllBytes( Paths.get(args[0]) ) ); // túlzott memóriafoglalás: 164 MB -> 664 MB
            //String str2 = Files.readString(Paths.get(args[0])); // only Java 11
            //String str3 = FileUtils.readFileToString(args[0], "utf-8"); // apache
            //String str4 = new Scanner(new File(args[0])).useDelimiter("\\Z").next(); // irreális memóriafoglalás: 164 MB -> 2086 MB

            /*BufferedReader buf = new BufferedReader(new InputStreamReader(new FileInputStream(args[0])));
            StringBuilder sb = new StringBuilder();
            String line = "";
            while ( (line = buf.readLine()) != null){
                sb.append(line).append("\n");
            }*/ // 164 MB-> 808 MB & java.lang.NullPointerException

            /*BufferedReader br = new BufferedReader(new FileReader(args[0]), 8192 * 8192);
            StringBuilder sb = new StringBuilder();
            String thisLine="";
            while ((thisLine = br.readLine()) != null) {
                sb.append(thisLine).append("\n");
            }*/ // 164 MB -> 1112 MB

            //FileReader fileReader = new FileReader(new File(args[0])); ... while read() is -1
            //InputStreamReader isr = new InputStreamReader(new FileInputStream(args[0]),Charset.defaultCharset().name()); // 164 MB -> 340 MB
            //InputStreamReader isr = new InputStreamReader(new FileInputStream(args[0]),Charset.forName("ISO-8859-2")); // 164 MB -> 340 MB
            //InputStreamReader isr = new InputStreamReader(new FileInputStream(args[0]),StandardCharsets.UTF_8); // 164 MB -> 340 MB

            // input stream reader is closed

        } catch (Exception e) {
            //e.printStackTrace();
            System.out.println(e);
        }
        Thread.sleep(10000);
    }
}