The scanner reads the wrong data, the text file format is:
111，Smith，Sam, 40，10.50
330，Jones，Jennifer，30，10.00
The program is:
public class P3 {
public static void main(String[] args) {
String file=args[0];
File fileName = new File(file);
try {
Scanner sc = new Scanner(fileName).useDelimiter(", ");
while (sc.hasNextLine()) {
if (sc.hasNextInt( ) ){ int id = sc.nextInt();}
String lastName = sc.next();
String firstName = sc.next();
if (sc.hasNextInt( ) ){ int hours = sc.nextInt(); }
if (sc.hasNextFloat()){ float payRate=sc.nextFloat(); }
System.out.println(firstName);
}
sc.close();
} catch(FileNotFoundException e) {
System.out.println("Can't open file "
+ fileName + " ");
}
}
}
The output is:
40，10.50
330，Jones，Jennifer，30，10.00
It is supposed to be:
Sam
Jennifer
How do I fix it?
The problem is that your data isn't just delimited by commas. It is also delimited by line-endings, and also by Unicode character U+FF0C (FULLWIDTH COMMA).
I took your code, replaced the line
Scanner sc = new Scanner(fileName).useDelimiter(", ");
with
Scanner sc = new Scanner(fileName, "UTF-8").useDelimiter(", |\r\n|\n|\uff0c");
and then ran it. It produced the output it was supposed to.
The text , |\r\n|\n|\uff0c is a regular expression that matches either:
a comma followed by a space,
a carriage-return (\r) followed by a newline (\n),
a newline on its own,
a Unicode full-width comma (\uff0c).
These are the characters we want to delimit the text by. I've specified both types of line-ending as I'm not sure which line-endings your file uses.
I've also set the scanner to use the UTF-8 encoding when reading from the file. I don't know whether that will make a difference for you, but on my system UTF-8 isn't the default encoding so I needed to specify it.
First, please swap fileName and file. Next, I suggest you use a try-with-resources. Your variables need to be at a common scope if you intend to use them. Finally, when using hasNextLine() I would then call nextLine and you can split on optional white space and comma. That could look something like
String fileName = // ...
File file = new File(fileName);
try (Scanner sc = new Scanner(file)) {
while (sc.hasNextLine()) {
String line = sc.nextLine();
String[] arr = line.split("\\s*,\\s*");
int id = Integer.parseInt(arr[0]);
String lastName = arr[1];
String firstName = arr[2];
int hours = Integer.parseInt(arr[3]);
float payRate = Float.parseFloat(arr[4]);
System.out.println(firstName);
}
} catch (FileNotFoundException e) {
System.out.println("Can't open file " + fileName + " ");
e.printStackTrace();
}
Related
Is there any way for java.util.Scanner to include the newline escape character when reading from a file?
This is my code:
File myFile = new File("file.txt");
Scanner myReader = new Scanner(myFile);
String content = "";
while(myReader.hasNextLine()) {
content += myReader.nextLine();
}
System.out.println(content);
myReader.close();
When it reads from the file, it doesn't include '\n' or any new lines. Does anyone know how to do this?
Thanks
When it reads from the file, it doesn't include '\n' or any new lines.
Does anyone know how to do this?
You can add the new line explicitly as follows:
while(myReader.hasNextLine()) {
content += myReader.nextLine() + "\n";
}
I also recommend you use StringBuilder instead of String for appending in a loop.
StringBuilder content = new StringBuilder();
while (myReader.hasNextLine()) {
content.append(myReader.nextLine()).append(System.lineSeparator());
// or the following
// content.append(myReader.nextLine()).append('\n');
}
Check StringBuilder vs String concatenation in toString() in Java to learn more about it.
If you you just want to read in lines and the line terminator you can do it by changing the behavior of Scanner.next(). If you run the following it will take in the line and the new line terminator as one unit.
\\z is a regex directive that says to include the line terminator.
Scanner scan = new Scanner(System.in);
scan.useDelimiter("\\z");
for (int i = 0; i < 5; i++) {
String line = scan.next();
System.out.println(line + "on next line");
}
To read from a file, try this.
try {
Scanner scan = new Scanner(new File("f:/Datafile.txt"));
scan.useDelimiter("\\z");
while (scan.hasNextLine()) {
String line = scan.next();
System.out.print(line);
}
} catch (FileNotFoundException fe) {
fe.printStackTrace();
}
So I am creating a program which when called, will have input, go to a file and change the number assigned to the string called. For example:
The file would look like:
stone 0 wood 5 water 2 metal 5
and if "wood" was called, it would go into the file, find wood then send add one to the value to the right of wood, which would only change that value to 6, then saves the file.
I've looked around on the internet but couldn't really find much which is tailored to my specific problem. Its either changing an int to either one or the other, or changing all ints to something.
public class Main {
public static void main(String[] args) {
FileWriter fw;
BufferedReader reader;
StringBuffer ib;
String allBlockAndNull = "stone 0 wood 5 water 2 metal 5";
String strDir = "C:\\Users\\amdro\\Desktop\\test.txt";
File fileDir = new File(strDir);
//creates file it doesn't exist
try {
fw = new FileWriter(fileDir);
fw.write(allBlockAndNull);
fw.close();
} catch (IOException e) {
e.printStackTrace();
}finally {}
}
}
If you could expand from the above, that would be great!
This is a very simple and basic solution to your problem: It consists of reading the file, appending all changes to a string and overwriting the same file with the string.
Create a scanner to read your text file and initialise a new string variable
Scanner s = new Scanner(new File("fileName.txt"));
String line = "";
While there is still a character in the text file, get the word and the number
while(sc.hasNext()){
String word = s.next();
int number = s.nextInt();
Then, inside the while loop, use switch and case to check the word. For example, if word = "wood", append "wood" and the new number, newNumber to line
case "wood":
line += word + " " + newNumber + " ";
break;
The default will be appending the word and the old number, number
default:
line += word + " " + number + " ";
Finally, just create a FileWriter and a BufferedWriter to write line to the text file.
You can't add numbers to a value from a file because all the values are Strings but what you can do is replace the String value
public static void main(String[] args) throws IOException {
File file = new File("file.txt");//The file containing stone 0 wood 5 water 2 metal 5
BufferedReader reader = new BufferedReader(new FileReader(file));
String words = "", list = "";
while ((words = reader.readLine()) != null) {
list += words;
}
reader.close();
Scanner s = new Scanner(file);
if(list.contains("wood")) {
String replacedtext = list.replaceAll("wood 5", "wood 6");
FileWriter writer = new FileWriter("file.txt");
writer.write(replacedtext);
writer.close();
}
}
}
I write this code that can search for the some specific text (such as word) in the text file with scanner class, but i want also to replace (old text to the new text) in the same old text locuation.
i find in the internet that i must used replaceAll method like ( replaceAll(old, new); )
but it does't work with the scanner class.
This is my code, it just search (if it existed ) write new text in new line without change the old one.
Do i need to change the method (to get the data) form scanner to FileReader ??
File file = new File("C:\\Users....file.txt");
Scanner input = new Scanner(System.in);
System.out.println("Enter the content you want to change:");
String Uinput = input.nextLine();
System.out.println("You want to change it to:");
String Uinput2 = input.nextLine();
Scanner scanner = new Scanner(file).useDelimiter(",");
BufferedWriter writer = new BufferedWriter(new FileWriter(file, true));
while (scanner.hasNextLine()) {
String lineFromFile = scanner.next();
if (lineFromFile.contains(Uinput)) {
lineFromFile = Uinput2;
writer.write(lineFromFile);
writer.close();
System.out.println("changed " + Uinput + " tO " + Uinput2);
break;
}
else if (!lineFromFile.contains(Uinput)){
System.out.println("Don't found " + Uinput);
break;
}
}
You cannot read from a file, then write to that same file. You need 2 different files.
while (read line from input file) {
if (NOT matches your search pattern)
write line to output file.
else { // matches
write start of line to your search pattern.
write your replace string
write from end of search pattern to end of line.
}
}
Unless your replace string is the same size as your search string, yes, you'll have to use 2 files. Consider the file:
Blah
Blah
Blah
Now replace the letter 'a' with "The quick Brown Fox". If you replace the first line, you've overwritten the rest of the file. Now you can't read the 2nd line, so YES, you'll have to use 2 files.
Here's another answer based on #Sedrick comment and your code.
I'm adding it to your pseudo code.
File file = new File("C:\\Users....file.txt");
Scanner input = new Scanner(System.in);
System.out.println("Enter the content you want to change:");
String Uinput = input.nextLine();
System.out.println("You want to change it to:");
String Uinput2 = input.nextLine();
Scanner scanner = new Scanner(file).useDelimiter(",");
java.util.List<String> tempStorage = new ArrayList<>();
while (scanner.hasNextLine()) {
String lineFromFile = scanner.next();
tempStorage.add(lineFromFile);
}
// close input file here
// Open your write file here (same file = overwrite).
// now loop through temp storage searching for input string.
for (String currentLine : tempStorage ) {
if (!lcurrentLine.contains(Uinput)){
String temp = currentLine.replace(Uinput, Uinput2);
write a line using temp variable
} else { // not replaced
write a line using currentLine;
}
// close write file here
By the way, you'll have to encase the reads writes with try catch to trap for IOExceptions. That's how I knew it was pseudo code. There are plenty of examples for reading/writing a file on this web site. It's easy to search for.
My task is to read a text file in chunks of 64 characters, and use 2 different processes called Substitution and Column Transposition to encrypt it. Then, I have to decrypt it and write it out to another file.
I have written and tested out both processes of encrypting and decrypting and it worked wonderfully. But then I tried to loop the processes in case more than 64 characters were in the input file.
As a test case, I tried a 128 character input file. Unfortunately, the result only gives me the first 64 characters twice. I've tracked the scanner position and it goes beyond 64, but the characters read start back from 0. I'm not sure what the problem is.
Here is the relevant part of my code:
public static void main(String[] args) {
//Declare variables
Scanner console = new Scanner(System.in);
String inputFileName = null;
File inputFile = null;
Scanner in = null;
do
{
//Check if there are enough arguments
try
{
inputFileName = args[1];
}
catch (IndexOutOfBoundsException exception)
{
System.out.println("Not enough arguments.");
System.exit(1);
}
catch (Exception exception)
{
System.out.println("There was an error. Please try again.");
System.exit(1);
}
//Check if Input File is valid
try
{
inputFile = new File(inputFileName);
in = new Scanner(inputFile);
outputFile = new File(outputFileName);
out = new Scanner(outputFile);
}
catch (FileNotFoundException exception)
{
System.out.println("Could not find input file.");
System.exit(1);
}
catch (Exception exception)
{
System.out.println("There was an error. Please try again.");
System.exit(1);
}
} while (outputFileName != null && !inputFile.exists());
//Encryption
//Prepare patterns
String subPattern = CreateSubstitutionPattern(hash);
int[] transPattern = CreateTranspositionPattern(hash);
//Apply patterns
String textContent = "";
String applySub = "";
String applyTrans = "";
do
{
textContent = Read64Chars(in);
applySub = applySub + ApplySubstitutionPattern(textContent, subPattern);
applyTrans = applyTrans + ApplyTranspositionPattern(applySub, transPattern);
} while (in.hasNext());
//Decryption
String encryptContent = "";
Scanner encrypt = new Scanner(applyTrans);
String removeTrans = "";
String removeSub = "";
do
{
encryptContent = Read64Chars(encrypt);
System.out.println(applyTrans);
removeTrans = removeTrans + RemoveTranspositionPattern(encryptContent, transPattern);
removeSub = removeSub + RemoveSubstitutionPattern(removeTrans, subPattern);
} while (encrypt.hasNext());
console.close();
in.close();
encrypt.close();
System.out.println(removeSub); //For temporary testing
}
public static String Read64Chars (Scanner in)
{
String textContent = "";
in.useDelimiter("");
for (int x=0; x<64; x++)
{
if (in.hasNext())
{
textContent = textContent + in.next().charAt(0);
}
}
return textContent;
}
Do note that I have more variables to fill in args[0] and args[2] but I removed them for simplicity.
I would like to know if it is true that once a scanner reads a portion of it's input, it "consumes" it, and that portion gets removed. Does the scanner reset itself when declared again through a method? For example, does the declaration only point to the input source of the original scanner, or the actual scanner with its current properties?
encrypt is a diffrent Scanner from in, which you advance by 64 characters when you first call Read64Chars. So, encrypt starts at the first character when you call Read64Chars(encrypt). It seems like you want to use the same Scanner both times.
Also, in the future please name your functions starting with a lowercase letter. I felt dirty typing that... :)
A proper solution to get the whole encrypted text would be a code like this
public static String encryptedTextFile (Scanner in)
{
//ArrayList<String> stringBlocksOf64Chars = new ArrayList<String>();
StringBuilder encryptedTxt = new StringBuilder();
String currentTxt = "";
while (in.hasNextLine()) {
String line = currentTxt + in.nextLine();
currentTxt = "";
int i = 0;
for( ; i < line.length()/64 ; i++){
currentTxt = line.substring(i * 64, (i+1)*64);
//TODO - encrypt the text before adding it to the list
encryptedTxt.append(currentTxt);//encryptedTxt.append(encrypt(currentTxt));
}
currentTxt = line.substring(i * 64, line.length());
}
encryptedTxt.append(currentTxt);
/*for(String str : stringBlocksOf64Chars)
System.out.println(str);*/
return encryptedTxt.toString();
}
Your loop for (int x=0; x<64; x++) makes sure that you read only first 64 characters always and not the complete file. To get around that you should actually read whole file line by line.
The above code block follows this idea.
Steps to break down the logic.
Read the file line by line using scanner.
Break each line into chunks of 64 characters and encrypt the block 64 characters at a time
Generate encrypted text adding the encrypted 64 characters.
Whatever you do first break down the logic/steps you want to use in your code to make it simpler to understand or code.
Break the lines into 64 characters
I have a txt file containing words and their abbreviations that looks like this
one,1
two,2
you,u
probably,prob
...
I have read the txt file into a string splitting it and replacing the commas with spaces like so..
public String shortenWord( String inWord ) {
word = inWord;
String text = "";
try {
Scanner sc = new Scanner(new File("abbreviations.txt"));
while (sc.hasNextLine()) {
text = text + sc.next().replace(",", " ") + " ";
}
// System.out.println(text);
//System.out.println(word);
if (text.contains(word)) {
System.out.println(word);
}
else {
System.out.println("nope");
}
}
catch ( FileNotFoundException e ) {
System.out.println( e );
}
return text;
}
The user must input a word that they want abbreviated and it will return the abbreviated version of the word.
class testit{
public static void main(String[] args){
Shortener sh = new Shortener();
sh.shortenWord("you");
}
}
I have it returning the word they entered if it is found but i want it to return the word next to it in the file which would be the abbreviated version.
eg. printed string 'text' looks like ..
one 1 two 2 three 3 you u probably prob hello lo
I want them to be able to enter 'you' the program find 'you' and then prints 'u' which is the next string over separated by a space
Removing the comma achieves nothing, so don't do it.
I would first split:
String[] text = sc.next().split(",");
Then compare with the first part of the split:
if (text[0].equals(word))
and if true, return the second part of the split:
return text[1];
Part of the logic looks like below:
Map<String,String> myShortHand = new HashMap<String, String>();
Scanner sc = new Scanner(new File("abbreviations.txt"));
while (sc.hasNextLine()) {
String text[] = sc.next().split(",");
myShortHand.put(text[0],text[1]);
}
Now get the details from map like
myShortHand.get("one");