Develop Reference

Java Big File Sorter

I am doing an assignment for my class where I have a file that is 7 Mb. Essentially I am supposed to break it up into 2 phases.
Phase 1: I add each word from the file into an array list and sort it in alphabetical order. I then add every 100,000 words into 1 file, so I have 12 files in total with the naming convention as displayed below in code.
Phase 2: For every 2 files, I read one line from each file, and write which one comes first in alphabetical order into a new file (basically sort), until I eventually merge 2 files into 1 that is sorted. I do this in a loop, so that the number of files get halved each time while being sorted, so essentially I would have 7 MB all sorted into one file.
What I am having trouble with: For phase 2, I successfully read phase 1, but it seems that my files are all being copied repeatedly into multiple files, rather than being sorted and merged. I appreciate any help given, thank you.
File: It seems I cannot upload the .txt file, but the code should work so that any file with any number of lines can be merged, just the number of lines variable needs to be changed.
Summary: 1 Big big file unsorted, turns into multiple sorted files (ie. 12), first sort and merge turns it into 6 files, second sort and merge turns it into 3 files, third merge turns it into 2 files, and fourth merge turns it into 1 file big file again.
Code:
package Assignment11;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;
public class FileSorter_1
{
public static ArrayList<String> storyline = new ArrayList<String>();
public static int num_lines = 100000; //this number can be changed
public static int num_files_initial;
public static int num_files_sec;
public static void main(String[] args) throws IOException
{
phase1();
phase2();
}
public static void phase1() throws IOException
{
Scanner story = new Scanner(new File("Aesop_Shakespeare_Shelley_Twain.txt")); //file name
int f = 0;
while(story.hasNext())
{
int i = 0;
while(story.hasNext())
{
String temp = story.next();
storyline.add(temp);
i++;
if(i > num_lines)
{
break;
}
}
Collections.sort(storyline, String.CASE_INSENSITIVE_ORDER);
BufferedWriter write2file = new BufferedWriter(new FileWriter("temp_0_" + f + ".txt")); //initialze new file
for(int x = 0; x<num_lines;x++)
{
write2file.write(storyline.get(x));
write2file.newLine();
}
write2file.close();
f++;
}
num_files_initial = f;
}
public static void phase2() throws IOException
{
int file_n = 1;
int prev_fn = 0;
int t = 0;
int g = 0;
while(g<5)
{
System.out.println(num_files_initial);
if(t+1 > num_files_initial-1)
{
if(num_files_initial % 2 != 0)
{
BufferedWriter w = new BufferedWriter(new FileWriter("temp_"+file_n +"_" + g + ".txt"));
Scanner file1 = new Scanner(new File("temp_"+prev_fn +"_" + t + ".txt"));
String word1 = file1.next();
while(file1.hasNext())
{
w.write(word1);
w.newLine();
}
g++;
break;
}
num_files_initial = num_files_initial / 2 + num_files_initial % 2;
g = 0;
t = 0;
file_n++;
prev_fn++;
}
String s1="temp_"+file_n +"_" + g + ".txt";
String s2="temp_"+prev_fn +"_" + t + ".txt";
String s3="temp_"+prev_fn +"_" + (t+1) + ".txt";
System.out.println(s2);
System.out.println(s3);
BufferedWriter w = new BufferedWriter(new FileWriter(s1));
Scanner file1 = new Scanner(new File(s2));
Scanner file2 = new Scanner(new File(s3));
String word1 = file1.next();
String word2 = file2.next();
System.out.println(num_files_initial);
//System.out.println(t);
//System.out.println(g);
while(file1.hasNext() && file2.hasNext())
{
if(word1.compareTo(word2) == 1) //if word 1 comes first = 1
{
w.write(word1);
w.newLine();
file1.next();
}
if(word1.compareTo(word2) == 0) //if word 1 comes second = 0
{
w.write(word2);
w.newLine();
file2.next();
}
}
while(file1.hasNext())
{
w.write(word1);
w.newLine();
break;
}
while(file2.hasNext())
{
w.write(word2);
w.newLine();
break;
}
g++;
t+=2;
w.close();
file1.close();
file2.close();
}
}
}

After writing data into the new files you are not clearing the existing sorted array and that's why it is being copied into new files. Here are some fixes:
...
int f = 0;
while(story.hasNext())
{
// initilize the array here.
storyline = new ArrayList<>();
int i = 0;
while(story.hasNext())
{
String temp = story.next();
storyline.add(temp);
i++;
if(i > num_lines)
{
break;
}
}
Collections.sort(storyline, String.CASE_INSENSITIVE_ORDER);
BufferedWriter write2file = new BufferedWriter(new FileWriter("temp_0_" + f + ".txt")); //initialze new file
// instead of num_lines use i
for(int x = 0; x<i;x++)
{
write2file.write(storyline.get(x));
write2file.newLine();
}
write2file.close();
f++;
}
num_files_initial = f;
Hope this helps.

FileNotFoundException When entering a string after input prompt

I'm not sure if I'm not entering my code the right way, or where the error in my actual code is. I'm relatively new to "try" "catch" and when I run the coverage of my code in Java it shows that after I enter the inputted string it goes straight to the error. Their is more than one class for this code's purpose but the code doesn't run through all of the classes before the error. The purpose of the code is to enter information about students and through the code determine if they match together. This class specifically is the main class of the program. The problem comes when i enter a string like "Abey," and I'll get the error.
ERROR:
Please give the student name:
Abey
java.io.FileNotFoundException: Abey (The system cannot find the file specified)
MY CODE
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.NoSuchElementException;
import java.util.Scanner;
public class Match {
public static void main(String[] args) {
Student[] arr = new Student[100];
System.out.println("Please give the student name: ");
Scanner input = new Scanner(System.in);
String filename = input.next();
Scanner nameInput;
try {
nameInput = new Scanner(new FileReader(filename));
int i = 0;
while (nameInput.hasNextLine()) {
Scanner ab = new Scanner(nameInput.nextLine());
ab.useDelimiter("[\t-]");
String name = ab.next();
String gender = ab.next();
String date = ab.next();
Scanner birthDateReader = new Scanner(date);
birthDateReader.useDelimiter("-");
int month = birthDateReader.nextInt();
int day = birthDateReader.nextInt();
int year = birthDateReader.nextInt();
int quietTime = ab.nextInt();
int music = ab.nextInt();
int reading = ab.nextInt();
int chatting = ab.nextInt();
Date birthdate = new Date(month, day, year);
Preference pref = new Preference(quietTime, music, reading, chatting);
Student studentAdd = new Student(name, gender.charAt(0), birthdate, pref);
arr[i++] = studentAdd;
}
int max = i;
for (i = 0; i < max; i++) {
if (!arr[i].getMatch()) {
int bestScore = 0;
int bestMatch = 0;
for (int j = i + 1; j < max; j++) {
if (!arr[j].getMatch()) {
int tmp = arr[i].compare(arr[j]);
if (tmp > bestScore) {
bestScore = tmp;
bestMatch = j;
}
}
}
if (bestScore != 0) {
arr[i].setMatched(true);
arr[bestMatch].setMatched(true);
System.out.println(arr[i].getName() + " can match with " + arr[bestMatch].getName() + " with the score " + bestScore);
} else
if (!arr[i].getMatch())
System.out.println(arr[i].getName() + " Does not have any matches.");
}
}
input.close();
} catch (NoSuchElementException e) {
System.out.println(e);
} catch (FileNotFoundException e) {
System.out.println(e);
}
}
}

The process cannot find the Abey file relative to the working directory. Try to specify the full path:
File root = new File("/path/to/data/files");
...
String filename = ....;
File datafile = new File(root, filename);
try (FileReader reader = new FileReader(datafile)) {
....
}

The main Problem is, Program is searching as relative path. You need to provide the complete path of the file.
String completePath = "/opt/java/path/"
Scanner input = new Scanner(System.in);
String filename = input.next();
Scanner nameInput;
try {
nameInput = new Scanner (new FileReader(completePath+filename));
This will be the modified code for you.
Here completePath variable contains path of the folder on which you have stored files by student name.

JAVA - reading from text file, recognizing new lines

I have a task to read a text file with several lines, after that I need to count every character's UNICODE value, so the sum of "hello" is 532 and for "how are you" is 1059 and so on, every string begins on new line in the .txt document and so far so good.
But for every line I need to print only its own value, and the way my code works, it adds every line's value and I cant get my head around a way to stop it when the end of the lxtine comes so it looks something like:
*read line
*count char values
*add up
*print them
*start over for the next line, and so
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.lang.String;
import java.util.Arrays;
public class SumLines {
public static void main(String[] args) {
String filePath = "/home/lines.txt";
String readLine;
int sum = 0;
try (BufferedReader bufferedReader = new BufferedReader(new FileReader(filePath))) {
while ((readLine = bufferedReader.readLine()) != null) {
char[] array = new char[readLine.length()];
System.out.println(readLine);
for (int i = 0; i < readLine.length(); i++) {
Arrays.fill(array, readLine.trim().charAt(i));
sum += (int) array[i];
System.out.print(sum + " ");
}
}
} catch (IOException e) {
System.out.println("Error.\n Invalid or missing file.");
e.printStackTrace();
}
System.out.println("\n*** final " + sum);
}
}

If I understood correctly, for the input:
hello
how are you
You would like to get something like this as output:
hello 532
how are you 1059
*** final 1591
For this, you need to make some modifications to your code:
In addition to calculating the sum of characters values per line, keep another sum of the total of all lines
For each input line, print the line followed by the sum of character values
You don't need an array at all
It's better to trim the input line once, instead of for every character
Like this:
int total = 0;
try (BufferedReader bufferedReader = new BufferedReader(new FileReader(filePath))) {
String readLine;
while ((readLine = bufferedReader.readLine()) != null) {
String trimmed = readLine.trim();
int sum = 0;
for (int i = 0; i < trimmed.length(); i++) {
sum += (int) trimmed.charAt(i);
}
System.out.println(readLine + " " + sum);
total += sum;
}
} catch (IOException e) {
System.out.println("Error.\n Invalid or missing file.");
e.printStackTrace();
}
System.out.println("\n*** final " + total);

After your for loop, set sum to 0. If you want to print the total sum, then you need another variable, say t.
Like this:
for (int i = 0; i < readLine.length(); i++) {
Arrays.fill(array, readLine.trim().charAt(i));
sum += (int) array[i];
System.out.print(sum + " ");
}
t=t+sum;
sum=0;
Then print t at the end.

A simple solution would be to limit the scope of the sum variable. That way, values will not persist between runs:
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.lang.String;
import java.util.Arrays;
public class SumLines {
public static void main(String[] args) {
String filePath = "/home/lines.txt";
String readLine;
int totalSum = 0;
try (BufferedReader bufferedReader = new BufferedReader(new FileReader(filePath))) {
String readLine;
while ((readLine = bufferedReader.readLine()) != null) {
int sum = 0;
for (int i = 0; i < readLine.length(); i++) {
sum += (int) readLine.charAt(i);
}
System.out.println(readLine + ": " + sum);
totalSum += sum;
}
} catch (IOException e) {
System.out.println("Error.\n Invalid or missing file.");
e.printStackTrace();
}
System.out.println("\n*** final " + totalSum);
}
}
Also, you don't have to use such complicated stuff just to get the Unicode value of a char. I made some improvements.

Have two variables, one for final sum and one for line sum.
public class SumLines {
public static void main(String[] args) {
String filePath = "/home/lines.txt";
String readLine;
int totalSum = 0;
int lineSum = 0
try (BufferedReader bufferedReader = new BufferedReader(new FileReader(filePath))) {
while ((readLine = bufferedReader.readLine()) != null) {
char[] array = new char[readLine.length()];
System.out.println(readLine);
for (int i = 0; i < readLine.length(); i++) {
Arrays.fill(array, readLine.trim().charAt(i));
lineSum += (int) array[i];
System.out.print(lineSum + " ");
}
totalSum += lineSum + totalSum;
lineSum = 0;
}
} catch (IOException e) {
System.out.println("Error.\n Invalid or missing file.");
e.printStackTrace();
}
System.out.println("\n*** final " + totalSum);
}
}

How can I make this Java read the whole last line, and not just each byte at a time?

I have a simple Java IO program which reads from a text file of numbers that looks like this :
1
2
3
4
5
6
7
8
9
17
It's supposed to simply print the lines in this text file to the console, and then tell me what the last line was. But it's printing the last line, here 17, as just 7 -
Here's my code so far :
import java.lang.*;
import java.io.*;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ParentClass3{
static int lastLine = 0;
public static void main(String[] args) {
File file = new File("C:\\Java_Scratch_\\someFile.txt");
try {
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
try {
int i = sc.nextInt();
System.out.println(i);
} catch (Exception e) {
System.out.println (" here is the stack trace " + e.getStackTrace() );
System.out.println (" here is the stack trace " );
}
}
sc.close();
} // END big-outer-Try
catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
int i = ParentClass3.countLines("C:\\Java_Scratch_\\someFile.txt");
System.out.println("There are " + i + " lines");
}
catch (IOException ioe) {
System.out.print("ioe" + ioe.getStackTrace() );
}
}
// putting the count function
public static int countLines(String filename) throws IOException {
InputStream is = new BufferedInputStream(new FileInputStream(filename));
try {
byte[] c = new byte[1024];
int count = 0;
int readChars = 0;
int lastline = 0;
boolean empty = true;
while ( (readChars = is.read(c)) != -1) {
for (int i = 0; i < readChars; ++i){
Byte b = c[i];
int xx = b.intValue();
lastLine = xx;
if (c[i] == '\n'){
++count;
empty = true;
} else {
empty = false;
}
}
}
if (!empty) {
count++;
}
int asciiVal = lastLine;
int lastLine2 = Character.getNumericValue(asciiVal);
System.out.println("the last line was " + lastLine2);
return count;
} finally {
is.close();
}
}//END method countLines
// end-count_func
}
How would I fix it, so that it says "the last line was 17" , rather just just 7 ?

the methos nextLine() should work, although I don't remember if that input would be parsed to a String, I guess that wouldn't affect, but anyway...

Scanner will take user input but will not find the file

This is a program to read a file and print out the file with some of the text edited. The code will compile the issue is that it will read the users input but will say file is not found when the file is there. I feel like I am missing something. I am brand new at this so go easy on me.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class MainTest {
public static void main(String args[]) {
// if (args[0] != null)
readFile();
}
public static void readFile() { // Method to read file
Scanner inFile = null;
String out = "";
try {
Scanner input = new Scanner(System.in);
System.out.println("enter file name");
String filename = input.next();
File in = new File(filename); // ask for the file name
inFile = new Scanner(in);
int count = 0;
while (inFile.hasNextLine()) { // reads each line
String line = inFile.nextLine();
for (int i = 0; i < line.length(); i++) {
char ch = line.charAt(i);
out = out + ch;
if (ch == '{') {
count = count + 1;
out = out + " " + count;
} else if (ch == '}') {
out = out + " " + count;
if (count > 0) {
count = count - 1;
}
}
}
}
System.out.println(out);
} catch (FileNotFoundException exception) {
System.out.println("File not found.");
}
inFile.close();
}
}

You can use System.getProperty("user.dir") to find where Scanner looking to find your file. And you should be sure your file is located here.