I am trying to read data from a text file and then store it to an array. I assume that there is one word per line. I am getting a NoSuchElementException here:
while (s.hasNextLine())
{
text = text + s.next() + " ";
}
This is my code:
public class ReadNote
{
public static void main(String[]args)
{
String text = readString("CountryList.txt");
System.out.println(text);
String[] words = readArray("CountryList.txt");
for (int i = 0; i < words.length; i++)
{
System.out.println(words[i]);
}
}
public static String readString(String file)
{
String text = "";
try{
Scanner s = new Scanner(new File(file));
while (s.hasNextLine())
{
text = text + s.next() + " ";
}
} catch(FileNotFoundException e)
{
System.out.println("file not found ");
}
return text;
}
public static String[] readArray(String file)
{
int ctr = 0;
try {
Scanner s1 = new Scanner(new File(file));
while (s1.hasNextLine())
{
ctr = ctr+1;
s1.next();
}
String[] words = new String[ctr];
Scanner s2 = new Scanner(new File(file));
for ( int i = 0; i < ctr; i++)
{
words [i] = s2.next();
}
return words;
} catch (FileNotFoundException e) { }
return null;
}
}
Here is the message.
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1371)
at ReadNote.readString(ReadNote.java:29)
at ReadNote.main(ReadNote.java:13)
For the specific exception you are getting in readString:
while (s.hasNextLine()) {
text = text + s.next() + " ";
}
You need to either call s.hasNext() in the loop guard, or use s.nextLine() in the body.
As described in this answer.
You have a single extra newline at the end of your file.
hasNextLine() checks to see if there is another linePattern in the buffer.
hasNext() checks to see if there is a parseable token in the buffer, as separated by the scanner's delimiter.
You should modify your code to one of the following
while (s.hasNext()) {
text = text + s.next() + " ";
}
while (s.hasNextLine()) {
text = text + s.nextLine() + " ";
}
There are 2 issues with your code as far as I can tell:
You forgot to check hasNextLine() for your second Scanner s2.
When using Scanner you need to check if there is a next line with hasNextLine(), and it will return null at EOF.
You probably want s.nextLine() instead of s.next() in your while loop since you are checking while (s1.hasNextLine()). In general, you have to match your .hasNext... to your .next....
Related
This is some code that I found to help with reading in a 2D Array, but the problem I am having is this will only work when reading a list of number structured like:
73
56
30
75
80
ect..
What I want is to be able to read multiple lines that are structured like this:
1,0,1,1,0,1,0,1,0,1
1,0,0,1,0,0,0,1,0,1
1,1,0,1,0,1,0,1,1,1
I just want to essentially import each line as an array, while structuring them like an array in the text file.
Everything I have read says to use scan.usedelimiter(","); but everywhere I try to use it the program throws straight to the catch that replies "Error converting number". If anyone can help I would greatly appreciate it. I also saw some information about using split for the buffered reader, but I don't know which would be better to use/why/how.
String filename = "res/test.txt"; // Finds the file you want to test.
try{
FileReader ConnectionToFile = new FileReader(filename);
BufferedReader read = new BufferedReader(ConnectionToFile);
Scanner scan = new Scanner(read);
int[][] Spaces = new int[10][10];
int counter = 0;
try{
while(scan.hasNext() && counter < 10)
{
for(int i = 0; i < 10; i++)
{
counter = counter + 1;
for(int m = 0; m < 10; m++)
{
Spaces[i][m] = scan.nextInt();
}
}
}
for(int i = 0; i < 10; i++)
{
//Prints out Arrays to the Console, (not needed in final)
System.out.println("Array" + (i + 1) + " is: " + Spaces[i][0] + ", " + Spaces[i][1] + ", " + Spaces[i][2] + ", " + Spaces[i][3] + ", " + Spaces[i][4] + ", " + Spaces[i][5] + ", " + Spaces[i][6]+ ", " + Spaces[i][7]+ ", " + Spaces[i][8]+ ", " + Spaces[i][9]);
}
}
catch(InputMismatchException e)
{
System.out.println("Error converting number");
}
scan.close();
read.close();
}
catch (IOException e)
{
System.out.println("IO-Error open/close of file" + filename);
}
}
I provide my code here.
public static int[][] readArray(String path) throws IOException {
//1,0,1,1,0,1,0,1,0,1
int[][] result = new int[3][10];
BufferedReader reader = new BufferedReader(new FileReader(path));
String line = null;
Scanner scanner = null;
line = reader.readLine();
if(line == null) {
return result;
}
String pattern = createPattern(line);
int lineNumber = 0;
MatchResult temp = null;
while(line != null) {
scanner = new Scanner(line);
scanner.findInLine(pattern);
temp = scanner.match();
int count = temp.groupCount();
for(int i=1;i<=count;i++) {
result[lineNumber][i-1] = Integer.parseInt(temp.group(i));
}
lineNumber++;
scanner.close();
line = reader.readLine();
}
return result;
}
public static String createPattern(String line) {
char[] chars = line.toCharArray();
StringBuilder pattern = new StringBuilder();;
for(char c : chars) {
if(',' == c) {
pattern.append(',');
} else {
pattern.append("(\\d+)");
}
}
return pattern.toString();
}
The following piece of code snippet might be helpful. The basic idea is to read each line and parse out CSV. Please be advised that CSV parsing is generally hard and mostly requires specialized library (such as CSVReader). However, the issue in hand is relatively straightforward.
try {
String line = "";
int rowNumber = 0;
while(scan.hasNextLine()) {
line = scan.nextLine();
String[] elements = line.split(',');
int elementCount = 0;
for(String element : elements) {
int elementValue = Integer.parseInt(element);
spaces[rowNumber][elementCount] = elementValue;
elementCount++;
}
rowNumber++;
}
} // you know what goes afterwards
Since it is a file which is read line by line, read each line using a delimiter ",".
So Here you just create a new scanner object passing each line using delimter ","
Code looks like this, in first for loop
for(int i = 0; i < 10; i++)
{
Scanner newScan=new Scanner(scan.nextLine()).useDelimiter(",");
counter = counter + 1;
for(int m = 0; m < 10; m++)
{
Spaces[i][m] = newScan.nextInt();
}
}
Use the useDelimiter method in Scanner to set the delimiter to "," instead of the default space character.
As per the sample input given, if the next row in a 2D array begins in a new line, instead of using a ",", multiple delimiters have to be specified.
Example:
scan.useDelimiter(",|\\r\\n");
This sets the delimiter to both "," and carriage return + new line characters.
Why use a scanner for a file? You already have a BufferedReader:
FileReader fileReader = new FileReader(filename);
BufferedReader reader = new BufferedReader(fileReader);
Now you can read the file line by line. The tricky bit is you want an array of int
int[][] spaces = new int[10][10];
String line = null;
int row = 0;
while ((line = reader.readLine()) != null)
{
String[] array = line.split(",");
for (int i = 0; i < array.length; i++)
{
spaces[row][i] = Integer.parseInt(array[i]);
}
row++;
}
The other approach is using a Scanner for the individual lines:
while ((line = reader.readLine()) != null)
{
Scanner s = new Scanner(line).useDelimiter(',');
int col = 0;
while (s.hasNextInt())
{
spaces[row][col] = s.nextInt();
col++;
}
row++;
}
The other thing worth noting is that you're using an int[10][10]; this requires you to know the length of the file in advance. A List<int[]> would remove this requirement.
EDIT: editted for clarity as to what I'm having trouble with. I'm not getting the right responses as its counting dupes. I HAVE to use RegEx, can use tokenizer however but I did not.
What I am trying to do here is, there is 5 input files. I need to calculate how many "USER DEFINED VARIABLES" there are. Please ignore the messy code, I'm just learning Java.
I replaced: everything within ( and ), all non-word characters, any statements such as int, main etc, any digit with a space infront of it, and any blank space with a new line then trim it.
This leaves me with a list that has a variety of strings which I will match with my RegEx. However, at this point, how make my count only include unique identifiers?
EXAMPLE:
For example, in the input file I have attached beneath the code, I am receiving
"distinct/unique identifiers: 10" in my output file, when it should be "distinct/unique identifiers: 3"
And for example, in the 5th input file I have attached, I should have "distinct/unique identifiers: 3" instead I currently have "distinct/unique identifiers: 6"
I cannot use Set, Map etc.
Any help is great! Thanks.
import java.util.*
import java.util.regex.*;
import java.io.*;
public class A1_123456789 {
public static void main(String[] args) throws IOException {
if (args.length < 1) {
System.out.println("Wrong number of arguments");
System.exit(1);
}
for (int i = 0; i < args.length; i++) {
FileReader jk = new FileReader(args[i]);
BufferedReader ij = new BufferedReader(jk);
FileWriter fw = null;
BufferedWriter bw = null;
String regex = "\\b(\\w+)(\\s+\\1\\b)+";
Pattern p = Pattern.compile("[_a-zA-Z][_a-zA-Z0-9]{0,30}");
String line;
int count = 0;
while ((line = ij.readLine()) != null) {
line = line.replaceAll("\\(([^\\)]+)\\)", " " );
line = line.replaceAll("[^\\w]", " ");
line = line.replaceAll("\\bint\\b|\\breturn\\b|\\bmain\\b|\\bprintf\\b|\\bif\\b|\\belse\\b|\\bwhile\\b", " ");
line = line.replaceAll(" \\d", "");
line = line.replaceAll(" ", "\n");
line = line.trim();
Matcher m = p.matcher(line);
while (m.find()) {
count++;
}
}
try {
String s1 = args[i];
String s2 = s1.replaceAll("input","output");
fw = new FileWriter(s2);
bw = new BufferedWriter(fw);
bw.write("distinct/unique identifiers: " + count);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (bw != null) {
bw.close();
}
if (fw != null) {
bw.close();
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
//This is the 3rd input file below.
int celTofah(int cel)
{
int fah;
fah = 1.8*cel+32;
return fah;
}
int main()
{
int cel, fah;
cel = 25;
fah = celTofah(cel);
printf("Fah: %d", fah);
return 0;
}
//This is the 5th input file below.
int func2(int i)
{
while(i<10)
{
printf("%d\t%d\n", i, i*i);
i++;
}
}
int func1()
{
int i = 0;
func2(i);
}
int main()
{
func1();
return 0;
}
Try this
LinkedList dtaa = new LinkedList();
String[] parts =line.split(" ");
for(int ii =0;ii<parts.length;ii++){
if(ii == 0)
dtaa.add(parts[ii]);
else{
if(dtaa.contains(parts[ii]))
continue;
else
dtaa.add(parts[ii]);
}
}
count = dtaa.size();
instead of
Matcher m = p.matcher(line);
while (m.find()) {
count++;
}
Amal Dev has suggested a correct implementation, but given the OP wants to keep Matcher, we have:
// Previous code to here
// Linked list of unique entries
LinkedList uniqueMatches = new LinkedList();
// Existing code
while ((line = ij.readLine()) != null) {
line = line.replaceAll("\\(([^\\)]+)\\)", " " );
line = line.replaceAll("[^\\w]", " ");
line = line.replaceAll("\\bint\\b|\\breturn\\b|\\bmain\\b|\\bprintf\\b|\\bif\\b|\\belse\\b|\\bwhile\\b", " ");
line = line.replaceAll(" \\d", "");
line = line.replaceAll(" ", "\n");
line = line.trim();
Matcher m = p.matcher(line);
while (m.find()) {
// New code - get this match
String thisMatch = m.group();
// If we haven't seen this string before, add it to the list
if(!uniqueMatches.contains(thisMatch))
uniqueMatches.add(thisMatch);
}
}
// Now see how many unique strings we have collected
count = uniqueMatches.size();
Note I haven't compiled this, but hopefully it works as is...
I am have a project that need to modify some text in the text file.
Like BB,BO,BR,BZ,CL,VE-BR
I need make it become BB,BO,BZ,CL,VE.
and HU, LT, LV, UA, PT-PT/AR become HU, LT, LV, UA,/AR.
I have tried to type some code, however the code fail to loop and also,in this case.
IN/CI, GH, KE, NA, NG, SH, ZW /EE, HU, LT, LV, UA,/AR, BB
"AR, BB,BO,BR,BZ,CL, CO, CR, CW, DM, DO,VE-AR-BR-MX"
I want to delete the AR in second row, but it just delete the AR in first row.
I got no idea and seeking for helps.
Please
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.util.Scanner;
public class tomy {
static StringBuffer stringBufferOfData = new StringBuffer();
static StringBuffer stringBufferOfData1 = stringBufferOfData;
static String filename = null;
static String input = null;
static String s = "-";
static Scanner sc = new Scanner(s);
public static void main(String[] args) {
boolean fileRead = readFile();
if (fileRead) {
replacement();
writeToFile();
}
System.exit(0);
}
private static boolean readFile() {
System.out.println("Please enter your files name and path i.e C:\\test.txt: ");
filename = "C:\\test.txt";
Scanner fileToRead = null;
try {
fileToRead = new Scanner(new File(filename));
for (String line; fileToRead.hasNextLine()
&& (line = fileToRead.nextLine()) != null;) {
System.out.println(line);
stringBufferOfData.append(line).append("\r\n");
}
fileToRead.close();
return true;
} catch (FileNotFoundException ex) {
System.out.println("The file " + filename + " could not be found! "+ ex.getMessage());
return false;
} finally {
fileToRead.close();
return true;
}
}
private static void writeToFile() {
try {
BufferedWriter bufwriter = new BufferedWriter(new FileWriter(
filename));
bufwriter.write(stringBufferOfData.toString());
bufwriter.close();
} catch (Exception e) {// if an exception occurs
System.out.println("Error occured while attempting to write to file: "+ e.getMessage());
}
}
private static void replacement() {
System.out.println("Please enter the contents of a line you would like to edit: ");
String lineToEdit = sc.nextLine();
int startIndex = stringBufferOfData.indexOf(lineToEdit);
int endIndex = startIndex + lineToEdit.length() + 2;
String getdata = stringBufferOfData.substring(startIndex + 1, endIndex);
String data = " ";
Scanner sc1 = new Scanner(getdata);
Scanner sc2 = new Scanner(data);
String lineToEdit1 = sc1.nextLine();
String replacementText1 = sc2.nextLine();
int startIndex1 = stringBufferOfData.indexOf(lineToEdit1);
int endIndex1 = startIndex1 + lineToEdit1.length() + 3;
boolean test = lineToEdit.contains(getdata);
boolean testh = lineToEdit.contains("-");
System.out.println(startIndex);
if (testh = true) {
stringBufferOfData.replace(startIndex, endIndex, replacementText1);
stringBufferOfData.replace(startIndex1, endIndex1 - 2,
replacementText1);
System.out.println("Here is the new edited text:\n"
+ stringBufferOfData);
} else {
System.out.println("nth" + stringBufferOfData);
System.out.println(getdata);
}
}
}
I wrote a quick method for you that I think does what you want, i.e. remove all occurrences of a token in a line, where that token is embedded in the line and is identified by a leading dash.
The method reads the file and writes it straight out to a file after editing for the token. This would allow you to process a huge file without worrying about about memory constraints.
You can simply rename the output file after a successful edit. I'll leave it up to you to work that out.
If you feel you really must use string buffers to do in memory management, then grab the logic for the line editing from my method and modify it to work with string buffers.
static void onePassReadEditWrite(final String inputFilePath, final String outputPath)
{
// the input file
Scanner inputScanner = null;
// output file
FileWriter outputWriter = null;
try
{
// open the input file
inputScanner = new Scanner(new File(inputFilePath));
// open output file
File outputFile = new File(outputPath);
outputFile.createNewFile();
outputWriter = new FileWriter(outputFile);
try
{
for (
String lineToEdit = inputScanner.nextLine();
/*
* NOTE: when this loop attempts to read beyond EOF it will throw the
* java.util.NoSuchElementException exception which is caught in the
* containing try/catch block.
*
* As such there is NO predicate required for this loop.
*/;
lineToEdit = inputScanner.nextLine()
)
// scan all lines from input file
{
System.out.println("START LINE [" + lineToEdit + "]");
// get position of dash in line
int dashInLinePosition = lineToEdit.indexOf('-');
while (dashInLinePosition != -1)
// this line has needs editing
{
// split line on dash
String halfLeft = lineToEdit.substring(0, dashInLinePosition);
String halfRight = lineToEdit.substring(dashInLinePosition + 1);
// get token after dash that is to be removed from whole line
String tokenToRemove = halfRight.substring(0, 2);
// reconstruct line from the 2 halves without the dash
StringBuilder sb = new StringBuilder(halfLeft);
sb.append(halfRight.substring(0));
lineToEdit = sb.toString();
// get position of first token in line
int tokenInLinePosition = lineToEdit.indexOf(tokenToRemove);
while (tokenInLinePosition != -1)
// do for all tokens in line
{
// split line around token to be removed
String partLeft = lineToEdit.substring(0, tokenInLinePosition);
String partRight = lineToEdit.substring(tokenInLinePosition + tokenToRemove.length());
if ((!partRight.isEmpty()) && (partRight.charAt(0) == ','))
// remove prefix comma from right part
{
partRight = partRight.substring(1);
}
// reconstruct line from the left and right parts
sb.setLength(0);
sb = new StringBuilder(partLeft);
sb.append(partRight);
lineToEdit = sb.toString();
// find next token to be removed from line
tokenInLinePosition = lineToEdit.indexOf(tokenToRemove);
}
// handle additional dashes in line
dashInLinePosition = lineToEdit.indexOf('-');
}
System.out.println("FINAL LINE [" + lineToEdit + "]");
// write line to output file
outputWriter.write(lineToEdit);
outputWriter.write("\r\n");
}
}
catch (java.util.NoSuchElementException e)
// end of scan
{
}
finally
// housekeeping
{
outputWriter.close();
inputScanner.close();
}
}
catch(FileNotFoundException e)
{
e.printStackTrace();
}
catch(IOException e)
{
inputScanner.close();
e.printStackTrace();
}
}
[EDITED} Ok I get it, let me reformulate. numVol is 45 and the contents of the file is
54;a;23;c;de;56
23;d;24;c;h;456
45;87;c;y;535
432;42;h;h;543
but I still can't fix my problem, with this it return 543. so what im trying to do is return line when its equals numVol but check only the first number of a line.
I'm having trouble comparing two strings. Let's say I have a .csv file with the following content: 54;a;b;c;de and that numVol value is 54. the method should be returning 54 but for some reason it doesnt enter in the "if" and it return "de".
public static String test(int numVol)throws Exception{
File file = new File("test.csv");
Scanner scanner = new Scanner(file);
scanner.useDelimiter(";");
String line = "";
String sNumVol = ""+numVol; //create a string with numVol value in it
while (scanner.hasNext()){
line = scanner.next();
if(line.equals(sNumVol)){
scanner.close();
return line;
}
}
scanner.close();
return line;
}
The problem is that now that you've told Scanner to use ; as a delimiter, it's not using whitespace as a delimiter anymore. So the token being tested against "45" isn't "45", it's "456\n45" (the end of the previous line, the newline, and the beginning of the next line), which isn't a match.
Change your useDelimiter line to use both semicolons and whitespace as your delimiters:
scanner.useDelimiter("[;\\s]");
...and then the scanner sees the "456" and the "45" separately, and matches the "45".
This code:
import java.util.*;
import java.io.*;
public class Parse {
public static final void main(String[] args) {
try {
String result = test(45);
System.out.println("result = " + result);
}
catch (Exception e) {
System.out.println("Exception");
}
}
public static String test(int numVol)throws Exception{
File file = new File("test.csv");
Scanner scanner = new Scanner(file);
scanner.useDelimiter("[;\\s]"); // <==== Change is here
String line = "";
String sNumVol = ""+numVol;
while (scanner.hasNext()){
line = scanner.next();
if(line.equals(sNumVol)){
scanner.close();
return line;
}
}
scanner.close();
return line;
}
}
With this test.csv:
54;a;23;c;de;56
23;d;24;c;h;456
45;87;c;y;535
432;42;h;h;543
Shows this:
$ java Parse
result = 45
The way to find the answer to this problem was simply to walk through the code with a debugger and watch the value of line, or (if for some reason you don't have a debugger?!), insert a System.out.println("line = " + line); statement into the loop to see what was being compared. For instance, if you insert a System.out.println("line = " + line); above the line = scanner.next(); line above and you just use ";" as the delimiter:
import java.util.*;
import java.io.*;
public class Parse {
public static final void main(String[] args) {
try {
String result = test(45);
System.out.println("result = " + result);
}
catch (Exception e) {
System.out.println("Exception");
}
}
public static String test(int numVol)throws Exception{
File file = new File("test.csv");
Scanner scanner = new Scanner(file);
scanner.useDelimiter(";"); // <== Just using ";"
String line = "";
String sNumVol = ""+numVol;
while (scanner.hasNext()){
line = scanner.next();
System.out.println("line = [[" + line + "]]");
if(line.equals(sNumVol)){
scanner.close();
return line;
}
}
scanner.close();
return line;
}
}
You see this:
$ java Parse
line = [[54]]
line = [[a]]
line = [[23]]
line = [[c]]
line = [[de]]
line = [[56
23]]
line = [[d]]
line = [[24]]
line = [[c]]
line = [[h]]
line = [[456
45]]
line = [[87]]
line = [[c]]
line = [[y]]
line = [[535
432]]
line = [[42]]
line = [[h]]
line = [[h]]
line = [[543
]]
result = 543
...which helps visualize the problem.
I am trying to create a program which will read a file and check whether the text is a palindrome or not. The code compiles, but doesnt really work.
The problem is I dont know how to break a complete token into characters or assign it to a string in order to use string's length to push(enqueue) each letter or digit into the stack(queue). Can anyone suggest a solution for this?
public static void main(String [] args) throws IOException{
StackReferenceBased stack = new StackReferenceBased();
QueueReferenceBased queue = new QueueReferenceBased();
Scanner s = null;
String fileName=args[0]+".txt";
int symbols = 0;
int lettersAndDigits =0;
int matches = 0;
try{
s = new Scanner(new File(fileName));
while(s.hasNext()){
String current = s.next();
for(int i=0;i<current.length();i++){
char temp = s.next().charAt(i);
if(Character.isLetterOrDigit(temp)){
stack.push(temp);
queue.enqueue(temp);
lettersAndDigits++;
}
else {
symbols++;
}
}
}
System.out.println("There are: " + " "+ symbols + " " +"symbols and " + " "+lettersAndDigits + " "+ "digits/letters");
}
catch (FileNotFoundException e) {
System.out.println("Could not open the file:" + args[0]);
} //catch (Exception e) {
//System.out.println("ERROR copying file");
finally {
if(s != null){
s.close();
}
}
while (!stack.isEmpty()){
if(!stack.pop().equals(queue.dequeue())){
System.out.println("not pali");
break;
}
else {
++matches;
}
}
if(matches==lettersAndDigits){
System.out.print("pali");
}
}
Instead of
char temp = s.next().charAt(i);
you need
char temp = current.charAt(i);
By calling s.next() you read the next token from the file and try to access the ith element of that token based on the first string's (current) length, which will lead to exceptions if the tokens read are shorter than the first stoken