Develop Reference

Reading data and storing in array Java

I am writing a program which will allow users to reserve a room in a hotel (University Project). I have got this problem where when I try and read data from the file and store it in an array I receive a NumberFormatException.
I have been stuck on this problem for a while now and cannot figure out where I am going wrong. I've read up on it and apparently its when I try and convert a String to a numeric but I cannot figure out how to fix it.
Any suggestions, please?
This is my code for my reader.
FileReader file = new FileReader("rooms.txt");
Scanner reader = new Scanner(file);
int index = 0;
while(reader.hasNext()) {
int RoomNum = Integer.parseInt(reader.nextLine());
String Type = reader.nextLine();
double Price = Double.parseDouble(reader.nextLine());
boolean Balcony = Boolean.parseBoolean(reader.nextLine());
boolean Lounge = Boolean.parseBoolean(reader.nextLine());
String Reserved = reader.nextLine();
rooms[index] = new Room(RoomNum, Type, Price, Balcony, Lounge, Reserved);
index++;
}
reader.close();
This is the error message
This is the data in my file which I am trying to read:

Change your while loop like this
while (reader.hasNextLine())
{
// then split reader.nextLine() data using .split() function
// and store it in string array
// after that you can extract data from the array and do whatever you want
}

You're trying to parse the whole line to Integer. You can read the whole line as a String, call
.split(" ")
on it. This will split the whole line into multiple values and put them into an array. Then you can grab each item from the array and parse separately as you intended.
Please avoid posting screenshots next time, use proper formatting and text so someone can easily copy your code or test data to IDE and reproduce the scenario.

Use next() instead of nextLine().

With Scanner one must use hasNextLine, nextLine, hasNext, next, hasNextInt, nextInt etcetera. I would do it as follows:
Using Path and Files - the newer more general classes i.o. File.
Files can read lines, here I use Files.lines which gives a Stream of lines, a bit like a loop.
Try-with-resources: try (AutoCloseable in = ...) { ... } ensures that in.close() is always called implicitly, even on exception or return.
The line is without line ending.
The line is split into words separated by one or more spaces.
Only lines with at least 6 words are handled.
Create a Room from the words.
Collect an array of Room-s.
So:
Path file = Paths.get("rooms.txt");
try (Stream<String> in = Files.lines(file)) {
rooms = in // Stream<String>
.map(line -> line.split(" +")) // Stream<String[]>
.filter(words -> words.length >= 6)
.map(words -> {
int roomNum = Integer.parseInt(words[0]);
String type = words[1];
double price = Double.parseDouble(words[2]);
boolean balcony = Boolean.parseBoolean(words[3]);
boolean lounge = Boolean.parseBoolean(words[4]);
String reserved = words[5];
return new Room(roomNum, type, price, balcony, lounge, reserved);
}) // Stream<Room>
.toArray(Room[]::new); // Room[]
}
For local variables use camelCase with a small letter in front.
The code uses the default character encoding of the system to convert the bytes in the file to java Unicode String. If you want all Unicode symbols,
you might store your list as Unicode UTF-8, and read them as follows:
try (Stream<String> in = Files.lines(file, StandardCharsets.UTF_8)) {
An other issue is the imprecise floating point double. You might use BigDecimal instead; it holds a precision:
BigDecimal price = new BigDecimal(words[2]);
It is however much more verbose, so you need to look at a couple of examples.

Regex to match a String with asterisk

I'm coding in Java and I want to split my string. I want to split it at.
/* sort */
Yes I plan to split a .java file that I have read as a string so I need it to include "/* sort */". I'm creating a code that sorts Arrays that are predefined in java class file.
Exactly that and do another split at
}
and then I wanted help how to go about splitting up the array since I'll be left with
an example would be this
final static String[] ANIMALS = new String[] /* sort */ { "eland", "antelope", "hippopotamus"};
My goal would be to sort that Array inside a .java file and replace it. This is my current code
private void editFile() throws IOException {
//Loads the whole Text or java file into a String
try (BufferedReader br = new BufferedReader(new FileReader(fileChoice()))) {
StringBuilder sb = new StringBuilder();
String line = br.readLine();
while (line != null) {
sb.append(line);
sb.append(System.lineSeparator());
line = br.readLine();
}
everything = sb.toString();
}
arrayCutOff = everything.split("////* sort *////");
for(int i = 0; i < arrayCutOff.length; i++){
System.out.println(arrayCutOff[i]);
}
}
This basically reads the whole .txt or .java file completely with the exact same formatting into one string. I planned to split it at /* sort */ and sort the array inside but I realized if I did that I probably can't replace it.

Considered your're using java 8 you might go this direction:
private void editFile() throws IOException {
List<String> lines = Files.readAllLines(Paths.get(fileChoice()));
String content = lines.stream().collect(Collectors.joining(System.lineSeparator()));
Stream.of(content.split(Pattern.quote("/* sort */"))).forEach(System.out::println);
}
However, the trick you're asking for is Pattern.quote, which dates back Java 5. It'll qoute a literal so it can be used as a literal in regExs and is a bit more convenient (and reliable I think) than wrestling around with backslashes...

Parse .csv File in java returns outofbounds exception

I have the following issue: I am trying to parse a .csv file in java, and store specifically 3 columns of it in a 2 Dimensional array. The Code for the method looks like this:
public static void parseFile(String filename) throws IOException{
FileReader readFile = new FileReader(filename);
BufferedReader buffer = new BufferedReader(readFile);
String line;
String[][] result = new String[10000][3];
String[] b = new String[6];
for(int i = 0; i<10000; i++){
while((line = buffer.readLine()) != null){
b = line.split(";",6);
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]); // Here is where the outofbounds exception occurs...
result[i][0] = b[0];
result[i][1] = b[3];
result[i][2] = b[4];
}
}
buffer.close();
}
I feel like I have to specify this: the .csv file is HUGE. It has 32 columns, and (almost) 10.000 entries (!).
When Parsing, I keep getting the following:
XXXXX CHUNKS OF SUCCESFULLY EXTRACTED CODE
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException:3
at ParseCSV.parseFile(ParseCSV.java:24)
at ParseCSV.main(ParseCSV.java:41)
However, I realized that SOME of the stuff in the file has a strange format e.g. some of the texts inside it for instance have newlines in them, but there is no newline character involved in any way. However, if I delete those blank lines manually, the output generated (before the error message is prompted) adds the stuff to the array up until the next blank line ...
Does anyone have an idea how to fix this? Any help would be greately appreciated...

Your first problem is that you probably have at least one blank line in your csv file. You need to replace:
b = line.split(";", 6);
with
b = line.split(";");
if(b.length() < 5){
System.err.println("Warning, line has only " + b.length() +
"entries, so skipping it:\n" + line);
continue;
}
If your input can legitimately have new lines or embedded semi-colons within your entries, that is a more complex parsing problem, and you are probably better off using a third-party parsing library, as there are several very good ones.
If your input is not supposed to have new lines in it, the problem probably is \r. Windows uses \r\n to represent a new line, while most other systems just use \n. If multiple people/programs edited your text file, it is entirely possible to end up with stray \r by themselves, which are not easily handled by most parsers.
A way to easily check if that's your problem is before you split your line, do
line = line.replace("\r","").
If this is a process you are repeating many times, you might need to consider using a Scanner (or library) instead to get more efficient text processing. Otherwise, you can make do with this.

When you have new lines in your CSV file, after this line
while((line = buffer.readLine()) != null){
variable line will have not a CSV line but just some text without ;
For example, if you have file
column1;column2;column
3 value
after first iteration variable line will have
column1;column2;column
after second iteration it will have
3 value
when you call "3 value".split(";",6) it will return array with one element. and later when you call b[3] it will throw exception.
CSV format has many small things, to implement which you will spend a lot of time. This is a good article about all possible csv examples
http://en.wikipedia.org/wiki/Comma-separated_values#Basic_rules_and_examples
I would recommend to you some ready CSV parsers like this
https://commons.apache.org/proper/commons-csv/apidocs/org/apache/commons/csv/CSVParser.html

String's split(pattern, limit) method returns an array sized to the number of tokens found up to the the number specified by the limit parameter. Limit is the maximum, not the minimum number of array elements returned.
"1,2,3" split with (",", 6) with return an array of 3 elements: "1", "2" and "3".
"1,2,3,4,5,6,7" will return 6 elements: "1", "2", "3", "4", "5" and ""6,7" The last element is goofy because the split method stopped splitting after 5 and returned the rest of the source string as the sixth element.
An empty line is represented as an empty string (""). Splitting "" will return an array of 1 element, the empty string.
In your case, the string array created here
String[] b = new String[6];
and assigned to b is replaced by the the array returned by
b = line.split(";",6);
and meets it's ultimate fate at the hands of the garbage collector unseen and unloved.
Worse, in the case of the empty lines, it's replaced by a one element array, so
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]);
blows up when trying to access b[3].
Suggested solution is to either
while((line = buffer.readLine()) != null){
if (line.length() != 0)
{
b = line.split(";",6);
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]); // Here is where the outofbounds exception occurs...
...
}
or (better because the previous could trip over a malformed line)
while((line = buffer.readLine()) != null){
b = line.split(";",6);
if (b.length() == 6)
{
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]); // Here is where the outofbounds exception occurs...
...
}
You might also want to think about the for loop around the while. I don't think it's doing you any good.
while((line = buffer.readLine()) != null)
is going to read every line in the file, so
for(int i = 0; i<10000; i++){
while((line = buffer.readLine()) != null){
is going to read every line in the file the first time. Then it going to have 9999 attempts to read the file, find nothing new, and exit the while loop.
You are not protected from reading more than 10000 elements because the while loop because the while loop will read a 10001th element and overrun your array if there are more than 10000 lines in the file. Look into replacing the big array with an arraylist or vector as they will size to fit your file.

Please check b.length>0 before accessing b[].

Empty array after reading text file

It's fixed! Thanks to Edgar Boda.
I created a class that should read a text file and put that into an array:
private static String[] parts;
public static void Start() throws IOException{
InputStream instream = new FileInputStream("Storyline.txt");
InputStreamReader inputreader = new InputStreamReader(instream);
BufferedReader buffreader = new BufferedReader(inputreader);
int numberOfLines=0, numberOfActions;
String line = null, input="";
while((line=buffreader.readLine())!=null){
line=buffreader.readLine();
input+=line;
}
parts=input.split(";");
}
But, when I try and output the array, it only contains one string. The last from the file, that I put in.
Here's the file I read from:
0;0;
Hello!;
Welcome!To this.;
56;56;
So;
I think it's something in the loop; but trying to put parts[number] in there doesn't work... Any suggestions?

You want to read the whole file into an String first maybe:
String line = null;
String input = "";
while((line=buffreader.readLine())!=null){
input += line;
}
parts = input.split(";");

You are overwriting the string array parts in every iteration of your while loop, so that's why it only contains the last line.
To store the entire file contents, with fields split, you'll need a 2-dimensional array, not a 1-dimensional array. Assuming there are 5 lines in the file:
private static String[][] parts = new String[5][];
Then assign each split array to an element of parts each loop:
parts[i++]=line.split(";"); // Assuming you define "i" for the line number
Also, split by default discards trailing empty tokens. To retain them, use the two-arg overload of split that takes a limit parameter. Pass a negative number to retain all tokens.
parts[i++] = line.split(";", -1);

It will only contain the last line; you are reassigning parts every time:
parts = line.split(";");
This trashes the previous reference and reassigns a reference to a new array to it. A better way might be to use a StringBuilder and append the lines and then split later:
StringBuilder stringBuilder = new StringBuilder();
while((line=buffreader.readLine())!=null){
stringBuilder.append(line);
}
parts = stringBuilder.toString().split(";");
This way you will get everything you want in one array. If you want to split everything such that you have one array per line, you will need parts to be a two-dimensional array. But the drawback is that you will need to know how many lines will be there in the file. Instead, you can use List<String[]> to keep track of your arrays:
List<String[]> lineParts = new ArrayList<String[]>();
while((line=buffreader.readLine())!=null){
lineParts.add(line.split(";"));
}

Storing input from text file

My question is quite simple, I want to read in a text file and store the first line from the file into an integer, and every other line of the file into a multi-dimensional array. The way of which I was thinking of doing this would be of creating an if-statement and another integer and when that integer is at 0 store the line into the integer variable. Although this seems stupid and there must be a more simple way.
For example, if the contents of the text file were:
4
1 2 3 4
4 3 2 1
2 4 1 3
3 1 4 2
The first line "4", would be stored in an integer, and every other line would go into the multi-dimensional array.
public void processFile(String fileName){
int temp = 0;
int firstLine;
int[][] array;
try{
BufferedReader input = new BufferedReader(new FileReader(fileName));
String inputLine = null;
while((inputLine = input.readLine()) != null){
if(temp == 0){
firstLine = Integer.parseInt(inputLine);
}else{
// Rest goes into array;
}
temp++;
}
}catch (IOException e){
System.out.print("Error: " + e);
}
}

I'm intentionally not answering this to do it for you. Try something with:
String.split
A line that says something like array[temp-1] = new int[firstLine];
An inner for loop with another Integer.parseInt line
That should be enough to get you the rest of the way

Instead, you could store the first line of the file as an integer, and then enter a for loop where you loop over the rest of the lines of the file, storing them in arrays. This doesn't require an if, because you know that the first case happens first, and the other cases (array) happen after.

I'm going to assume that you know how to use file IO.
I'm not extremely experienced, but this is how I would think about it:
while (inputFile.hasNext())
{
//Read the number
String number = inputFile.nextLine();
if(!number.equals(" ")){
//Do what you need to do with the character here (Ex: Store into an array)
}else{
//Continue on reading the document
}
}
Good Luck.