Develop Reference

Read file using delimiter and add to array

I am trying to read from a text file that is in my project workspace then;
Create an object depending on the first element on the first line of the file
Set some variables within the object
Then add it to my arrayList
I seem to be reading the file ok but am struggling to create the different objects based off what the first element on each line in the text file is
Text file is like this
ul,1,gg,0,33.0
sl,2,hh,0,44.0
My expected result is to create an UltimateLanding object or StrongLanding object based on the first element in the text above file example
Disclaimer - I know the .equals is not correct to use in the IF statement, i've tried many ways to resolve this
My Code -
Edited -
It seems the program is now reading the file and correctly and adding to the array. However, it is only doing this for the first line in the file? There should be 2 objects created as there are 2 lines in the text file.
Scanner myFile = new Scanner(fr);
String line;
myFile.useDelimiter(",");
while (myFile.hasNext()) {
line = myFile.next();
if (line.equals("sl")) {
StrongLanding sl = new StrongLanding();
sl.setLandingId(Integer.parseInt(myFile.next()));
sl.setLandingDesc(myFile.next());
sl.setNumLandings(Integer.parseInt(myFile.next()));
sl.setCost(Double.parseDouble(myFile.next()));
landings.add(sl);
} else if (line.equals("ul")) {
UltimateLanding ul = new UltimateLanding();
ul.setLandingId(Integer.parseInt(myFile.next()));
ul.setLandingDesc(myFile.next());
ul.setNumLandings(Integer.parseInt(myFile.next()));
ul.setCost(Double.parseDouble(myFile.next()));
landings.add(ul);
}
}
TIA

There are multiple issues with your current code.
myFile.equals("sl") compares your Scanner object with a String. You would actually want to compare your read string line, not your Scanner object. So line.equals("sl").
nextLine() will read the whole line. So line will never be equal to "sl". You should split the line using your specified delimiter, then use the split parts to build your object. This way, you will not have to worry about newline in combination with next().
Currently, your evaluation of the read input is outside of the while loop, so you will read all the content of the file, but only evaluate the last line (currently). You should move the evaluation of the input and creation of your landing objects inside the while loop.
All suggestions implemented:
...
Scanner myFile = new Scanner(fr);
// no need to specify a delimiter, since you want to read line by line
String line;
String[] splitLine;
while (myFile.hasNextLine()) {
line = myFile.nextLine();
splitLine = line.split(","); // split the line by ","
if (splitLine[0].equals("sl")) {
StrongLanding sl = new StrongLanding();
sl.setLandingId(Integer.parseInt(splitLine[1]));
sl.setLandingDesc(splitLine[2]);
sl.setNumLandings(Integer.parseInt(splitLine[3]));
sl.setCost(Double.parseDouble(splitLine[4]));
landings.add(sl);
} else if (splitLine[0].equals("ul")) {
UltimateLanding ul = new UltimateLanding();
ul.setLandingId(Integer.parseInt(splitLine[1]));
ul.setLandingDesc(splitLine[2]);
ul.setNumLandings(Integer.parseInt(splitLine[3]));
ul.setCost(Double.parseDouble(splitLine[4]));
landings.add(ul);
}
}
...
However, if you don't want to read the contents line by line (due to whatever requirement you have), you can keep reading it via next(), but you have to specify the delimiter correctly:
...
Scanner myFile = new Scanner(fr);
String line; // variable naming could be improved, since it's not the line
myFile.useDelimiter(",|\\n"); // comma and newline as delimiters
while (myFile.hasNext()) {
line = myFile.next();
if (line.equals("sl")) {
StrongLanding sl = new StrongLanding();
sl.setLandingId(Integer.parseInt(myFile.next()));
sl.setLandingDesc(myFile.next());
sl.setNumLandings(Integer.parseInt(myFile.next()));
sl.setCost(Double.parseDouble(myFile.next()));
landings.add(sl);
} else if (line.equals("ul")) {
UltimateLanding ul = new UltimateLanding();
ul.setLandingId(Integer.parseInt(myFile.next()));
ul.setLandingDesc(myFile.next());
ul.setNumLandings(Integer.parseInt(myFile.next()));
ul.setCost(Double.parseDouble(myFile.next()));
landings.add(ul);
}
}
...

A solution.
List<Landing> landings = Files.lines(Paths.get("LandingsData.txt")).map(line -> {
String[] split = line.split(",");
if (split[0].equals("sl")) {
StrongLanding sl = new StrongLanding();
sl.setLandingId(Integer.parseInt(split[1]));
sl.setLandingDesc(split[2]);
sl.setNumLandings(split[3]);
sl.setCost(Double.parseDouble(split[4]));
return sl;
} else if (split[0].equals("ul")) {
UltimateLanding ul = new UltimateLanding();
ul.setLandingId(Integer.parseInt(split[1]));
ul.setLandingDesc(split[2]);
ul.setNumLandings(split[3]);
ul.setCost(Double.parseDouble(split[4]));
return ul;
}
return null;
}).filter(t -> t!= null).collect(Collectors.toList());

Ignore new lines while reading a file

I'm trying to read text inside a .txt document using console command java program < doc.txt. The program should look for words inside a file, and the file CAN contain empty new lines, so I've tried changing the while condition from:
while((s = in.nextLine()) != null)
to:
while((s = in.nextLine()) != "-1")
making it stop when it would have found -1 (I've also tried with .equals()), but it does not work. How can I tell my program to stop searching for words when there's no more text to examine? Otherwise it keeps stopping when it finds an empty string (newline alone or sequence of new lines).
I've only found solutions using BufferedReader, but I don't know how to use it in this situation where the file is being read by the console command java program < doc.txt.
I post the code inside the while, if it can be necessary:
while((s = in.nextLine()) != null) {
s = s.toLowerCase();
Scanner line = new Scanner(s);
a = line.next();
if(a.equals("word")) {
k++;
}
}

Proper way of figuring out when Scanner runs out of input is checking hasNextLine() condition. Use this loop to read a sequence of strings that includes empty lines:
Scanner in = new Scanner(System.in);
while(in.hasNextLine()) {
String s = in.nextLine();
System.out.println(s);
}
Demo.

Java - Read and storing in an array

I want to read the contents of a text file, split on a delimiter and then store each part in a separate array.
For example the-file-name.txt contains different string all on a new line:
football/ronaldo
f1/lewis
wwe/cena
So I want to read the contents of the text file, split on the delimiter "/" and store the first part of the string before the delimiter in one array, and the second half after the delimiter in another array. This is what I have tried to do so far:
try {
File f = new File("the-file-name.txt");
BufferedReader b = new BufferedReader(new FileReader(f));
String readLine = "";
System.out.println("Reading file using Buffered Reader");
while ((readLine = b.readLine()) != null) {
String[] parts = readLine.split("/");
}
} catch (IOException e) {
e.printStackTrace();
}
This is what I have achieved so far but I am not sure how to go on from here, any help in completing the program will be appreciated.

You can create two Lists one for the first part and se second for the second part :
List<String> part1 = new ArrayList<>();//create a list for the part 1
List<String> part2 = new ArrayList<>();//create a list for the part 2
while ((readLine = b.readLine()) != null) {
String[] parts = readLine.split("/");//you mean to split with '/' not with '-'
part1.add(parts[0]);//put the first part in ths list part1
part2.add(parts[1]);//put the second part in ths list part2
}
Outputs
[football, f1, wwe]
[ronaldo, lewis, cena]

Writing to a text file at a specific position Java

Suppose I have a file called "Bill.txt".
The format:
ItemType ItemName Price
Now I want to add a new Description field. This description must be written next to the price.
The problem is, how to determine the position where to write it.

Yeah I agree with user2085282. You could read in the file using:
BufferedReader in = new BufferedReader(new FileReader("Bill.txt"));
For each line, the Reader reads, add like a semicolon or some character that should not be in the original file. Then in array split the string based on that character.
while ((line = in.readLine()) != null) {
//string = line + semicolon
// then set an array to split(;)
}
Then in another loop have like result += array[i] + description;
Then write the string in a new file

Read text file and split each newline into a string array

So basically I'm reading a text file that has a bunch of lines. I need to extract certain lines from the text file and add those specific lines into string array. I've been trying to split each newLine with: "\n" , "\r". This did not work. I keep getting this error as well:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at A19010.main(A19010.java:47)
Here is the code:
Path objPath = Paths.get("dirsize.txt");
if (Files.exists(objPath)){
File objFile = objPath.toFile();
try(BufferedReader in = new BufferedReader(
new FileReader(objFile))){
String line = in.readLine();
while(line != null){
String[] linesFile = line.split("\n");
String line0 = linesFile[0];
String line1 = linesFile[1];
String line2 = linesFile[2];
System.out.println(line0 + "" + line1);
line = in.readLine();
}
}
catch(IOException e){
System.out.println(e);
}
}
else
{
System.out.println(
objPath.toAbsolutePath() + " doesn't exist");
}

String[] linesFile = new String[] {line}; // this array is initialized with a single element
String line0 = linesFile[0]; // fine
String line1 = linesFile[1]; // not fine, the array has size 1, so no element at second index
String line2 = linesFile[2];
You're creating a String[] linesFile with one element, line, but then trying to access elements at index 1 and 2. This will give you an ArrayIndexOutOfBoundsException
You're not actually splitting anything here. in.readLine();, as the method says, reads a full line from the file.
Edit: You can add lines (Strings) dynamically to a list instead of an array, since you don't know the size.
List<String> lines = new LinkedList<String>(); // create a new list
String line = in.readLine(); // read a line at a time
while(line != null){ // loop till you have no more lines
lines.add(line) // add the line to your list
line = in.readLine(); // try to read another line
}

readLine() method reads a entire line from the input but removes the newLine characters from it. When you split the line on \n character, you will not find one in the String. Hence, you get the exception.
Please, refer the answer in this link for more clarity.

You are initializing your String array with 1 element, namely line. linesFile[0] is therefore line and the rest of your array is out of bounds.

Try this:
String[] linesFile = line.split("SPLIT-CHAR-HERE");
if(linesFile.length >= 3)
{
String line0 = linesFile[0];
String line1 = linesFile[1];
String line2 = linesFile[2];
// further logic here
}else
{
//handle invalid lines here
}

You are using array to store the strings. Instead use ArrayList from Java as ArrayList are dynamically growing. after your reading operation completes convert it into array.
String line = in.readLine();
ArrayList<String> str_list = new ArrayList<String>();
String[] strArr = new String[str_list.size()];
while(line != null){
str_list.add(line);
line = in.readLine();
}
// at the end of the operation convert Arraylist to array
return str_list.toArray(strArr);

The issue here is that you are creating a new String array every time your parser reads in a new line. You then populate only the very first element in that String array with the line that is being read in with:
String[] linesFile = new String[] {line};
Since you create a new String[] with one element every single time your while loop runs from the top, you lose the values it stored from the previous iteration.
The solution is to use new String[]; right before you enter the while loop. If you don't know how to use ArrayList, then I suggest a while loop like this:
int numberOfLine = 0;
while (in.readLine() != null)
{
numberOfLine++;
}
String linesFile = new String[numberOfLine];
This will let you avoid using a dynamically resized ArrayList because you know how many lines your file contains from the above while loop. Then you would keep an additional counter (or resuse numberOfLine since we have no use for it anymore) so that you can populate this array:
numberOfLine = 0;
in = new BufferedReader(new FileReader(objFile)); // reset the buffer
while ((String line = in.readLine()) != null)
{
linesFile[numberOfLine] = line;
numberOfLine++;
}
At this point linesFile should be correctly populated with the lines in your file, such that linesFile[i] can be used to access the i'th line in the file.