how to insert a new line character in a string to PrintStream then use a scanner to re-read the file
The linefeed character \n
is not the line separator in certain operating systems (such as windows, where it's "\r\n") - my suggestion is that you use \r\n
instead, then it'll both see the line-break with only \n
and \r\n
, I've never had any problems using it.
Also, you should look into using a StringBuilder
instead of concatenating the String
in the while-loop at BookCatalog.toString()
, it is a lot more effective. For instance:
public String toString() {
BookNode current = front;
StringBuilder sb = new StringBuilder();
while (current!=null){
sb.append(current.getData().toString()+"\r\n ");
current = current.getNext();
}
return sb.toString();
}
Sara
Updated on July 21, 2020Comments
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Sara almost 4 years
I have several classes designed to simulation a book catalog. I have a book class (isbn, title, etc...), a BookNode class, a BookCatalog which is a LinkedList of books and a driver class (gui). My problem is that I have a toString() method in BookCatalog that supposed to return a String representation of all the books. The Book class also overrides toString(). I'm supposed to have each field of the book separated by a "tab" and each book separated by a "new line". When I try to use PrintStream to print the book catalog to a .txt file, the \n doesn't register.
I've tried to change it to System.getProperty(line.separator) which displays the bookcatalog correctly. But now, I have a problem where the Scanner will not read the file correctly and throws a "NoSuchElementException". How do I get the scanner to 1) Ignore the line.separator or 2) have printStream use \n?
Book.java
public String toString(){ return isbn+"\t"+lastName+"\t"+firstName+"\t"+title+"\t"+year+"\t"+ String.format("%.2f",price);
BookCatalog.java
public String toString() { BookNode current = front; String s=""; System.out.println(s); while (current!=null){ //each book is listed on separate line s+=current.getData().toString()+"\n ";//System.getProperty("line.separator") current = current.getNext(); } return s; }
Driver.java
public void loadDirectory() throws FileNotFoundException { if (f.exists()){ Scanner input = new Scanner(f); while (input.hasNextLine()){ String bookLine = input.nextLine(); processBookLine(bookLine); } } } public void processBookLine(String line){ Scanner input = new Scanner(line); String isbn = input.next(); String lastName = input.next(); String firstName = input.next(); String title = input.next(); while (input.hasNext() && !input.hasNextInt()){//while next token is not an integer title += " "+input.next(); } int year = input.nextInt(); double price = input.nextDouble(); Book book = Book.createBook(isbn, lastName, firstName, title, year, price); if (book!=null){ catalog.add(book); } }
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user207421 about 11 yearsIf you're claiming that
PrintStream
suppresses the\r
you are mistaken. The remainder of your question is not clear. -
Sara about 11 yearsI used the System.getProperty("line.separator") instead of \n so when i open the newly created file (from PrintStream) and tried to reread it (scanner), it will not process the line. I'm assuming that the "line.separator" is the reason why so I tried to save the character in another variable to bypass it but that didn't work either.
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user207421 about 11 yearsI don't see any reason why this should make any difference. Scanner handles \n, \r, and \r\n as line terminators already, and several others as well.
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ddmps about 10 years@EJP Scanner yes, but if you open a .txt on notepad with only \n in Windows, it will not register.
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AVA over 8 years@ddmps It inserts an extra line at the end! Please suggest how to handle it!
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ddmps over 8 years@AVA I do not see the issue with the "extra" line. See stackoverflow.com/a/729795/1690982.
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AVA over 8 years@ddmps Thanks for clarification with reference!
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iamjoshua over 6 yearsUsing "\r\n" instead of "\n" work just fine for me. Thanks alot. Upped!.