package textgen;

import java.io.BufferedWriter;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Random;

public class TextGen {

    private static final String PATH_SRC = "C:\\Documents and Settings\\User\\Рабочий стол\\src.txt";

    public static void main(String[] args) throws IOException {
        try (Writer writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(PATH_SRC), "Cp1251"))) {
            Random r = new Random();
//            for (int i = 1; i < 2_000_001; ++i) { //450Mb
//            for (int i = 1; i < 1_000_001; ++i) { //220Mb
            for (int i = 1; i < 70_001; ++i) { //14Mb
                for (int j = 0; j < 10; ++j) {
                    writer.write("слово_");
                    writer.write(Integer.toString(i));
                    writer.write('_');
                    for (int k = 7 + r.nextInt(5); k > 0; --k) {
                        writer.write('a' + r.nextInt(25));
                    }
                    writer.write('\t');
                }
                writer.write('\n');
            }
        }
    }
}

package readfile;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.ArrayList;

import static java.lang.System.*;
import static java.util.Arrays.copyOf;

public class ReadFile {

    /** максимальная длина слова */
    private static final int BUFFER_SIZE = 64_000;
    private static final String
            CHARSET  = "Cp1251",
//            CHARSET  = "UTF-8",
            PATH_SRC = "C:\\Documents and Settings\\User\\Рабочий стол\\src.txt";

    public static void main(String[] args) throws IOException {
//        readBytes();
        readChars();
    }

    private static void readChars() throws IOException {
        long time = nanoTime();

        ArrayList<String> arrayList;
        try (Reader reader = new BufferedReader(new InputStreamReader(new FileInputStream(PATH_SRC), CHARSET))) {
            arrayList = new ArrayList<>(700_000);
//            arrayList = new ArrayList<>(10_000_000);
//            arrayList = new ArrayList<>(20_000_000);
            int position = 0;
            char[] buffer = new char[BUFFER_SIZE];
            for (int readed; (readed = reader.read()) != -1;) {
                if (readed > 32) {
                    buffer[position++] = (char) readed;
                } else if (position > 0) {
                    arrayList.add(new String(buffer, 0, position));
                    position = 0;
                }
            }
        }

        time = nanoTime() - time;
        out.println(arrayList.size() + " слов");
        out.println("readChars : " + time / 1e6 + "ms");
    }

    private static void readBytes() throws IOException {
        long time = nanoTime();

        ArrayList<byte[]> arrayList;
        try (InputStream reader = new BufferedInputStream(new FileInputStream(PATH_SRC))) {
            arrayList = new ArrayList<>(700_000);
//            arrayList = new ArrayList<>(10_000_000);
//            arrayList = new ArrayList<>(20_000_000);
            int position = 0;
            byte[] buffer = new byte[BUFFER_SIZE];
            for (int readed; (readed = reader.read()) != -1;) {
                if (readed > 32) {
                    buffer[position++] = (byte) readed;
                } else if (position > 0) {
                    arrayList.add(copyOf(buffer, position));
                    position = 0;
                }
            }
        }

        time = nanoTime() - time;
        out.println(arrayList.size() + " слов");
        out.println("readBytes : " + time / 1e6 + "ms");
    }
}