So I have a text file that looks like this...
4234
Bob
6858
Joe
I am trying to read the file with java and insert the data into an array. I want to separate the data by that empty line (space). Here is the code that I have come up with to solve the issue, but I am not quite there.
public class Main {
public static void main(String[] args) {
// This name is used when saving the file
BufferedReader input;
String inputLine;
try {
input = new BufferedReader(new FileReader("test.txt"));
while ((inputLine = input.readLine()) != null) {
System.out.println(Arrays.toString(inputLine.split(" ")));
}
} catch (IOException e) {
System.out.println(e.getMessage());
System.exit(1);
}
}
}
The issue that I am coming across is that the output from the code above looks something like this
[4234]
[Bob]
[]
[6858]
[Joe]
The outcome that I would like to achieve, and for the life of me can't think of how to accomplish, is
[4234, Bob]
[6858, Joe]
I feel like with many things that it is a relatively simple code change; I am just not sure what that is.
You need:
2D array
Logic to keep track of where you are in the array position
If your Line is a Number/String
This sounds like hw :) so I wont be solving it, I will just help a bit.
String[][] myData = define your 2D array;
//You need to create a consumer. This is what will take the String line, figure out where to put it into your 2D array.
Consumer<String> processLine = (line) -> {
if(StringUtils.isNumeric(line)){
//Put into array[counter][1]
}
else{
//its a String
//Put into array[counter][0]
}
};
The below try/catch, Opens a File, Reads its Lines, and goes over each one in order (forEachOrdered), ignoring all empty lines, and send it to your processLine consumer.
try (Stream<String> lines = Files.lines(Paths.get("C:/example.txt"), Charset.defaultCharset())) {
lines.filter(line -> !line.isEmpty()).forEachOrdered(processLine);
}
catch (Exception e){
//Handle Exception
}
Used Apache StringUtils http://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html
IF you dont want to use any external Libs. You can probably do
Integer.parseInt(line) <-- If that throws an exception, its not a number
Your way of reading the file is not most convenient, in this case.. Scanner would have eased all this work; however, if you insist, that you want to use BufferedReader and FileReader, it's going to be a bit verbose, boilerplate and even ugly code, something like this:
public class Main {
public static void main(String[] args) {
// This name is used when saving the file
BufferedReader input;
String inputLine;
String answer = "";
try {
input = new BufferedReader(new FileReader("path\\to\\your\\test.txt"));
while ((inputLine = input.readLine()) != null) {
answer = answer + "[" + inputLine + ", ";
while ((inputLine = input.readLine()) != null && !inputLine.equals("")) {
answer += inputLine;
}
answer += "]";
System.out.println(answer);
answer = "";
}
} catch (IOException e) {
System.out.println(e.getMessage());
System.exit(1);
}
}
}
This code, with test.txt containing:
4234
Bob
6858
Joe
4234
John
5352
Martin
will output:
[4234, Bob]
[6858, Joe]
[4234, John]
[5352, Martin]
I don't know if it's an actual requirement for you to use arrays of strings, but the better way in the long run is to create a class.
class Person {
public String id;
public String name;
public String toString() { return String.format("[%s, %s]", id, name); }
}
(note: It's a bad idea to actually make the fields public, but this makes the code shorter. You should probably use getters and setters).
Now you can create Persons while reading the file.
List<Person> allInFile = new ArrayList<>();
try (BufferedReader reader = new BufferedReader(new FileReader("path\\to\\your\\test.txt"))) {
String line = reader.readLine();
while (line != null) {
line = line.trim();
// ignore empty lines
if (line.length() == 0) {
continue;
}
// this is an id; create a person and assign id
Person person = new Person();
person.id = line;
// read consecutive field, which is the name
person.name = reader.readLine();
// add the person to the list
allInFile.add(person);
}
}
allInFile.forEach(System.out::println);
Lots of improvements to be done on this, but the main point is to put the two data points into a class.
Try with this code:
it work only when file contains number followed by name otherwise pair would be different format
pair : [number, string]
public static void main(String[] args) {
BufferedReader input;
String inputLine;
List<String> pair = new ArrayList<String>();
List<String> list = new ArrayList<String>();
try {
input = new BufferedReader(new FileReader("Test.txt"));
while ((inputLine = input.readLine()) != null) {
if (!inputLine.isEmpty()) {
pair.add(inputLine);
}
if (pair.size() == 2) {
list.add(pair.toString());
pair.clear();
}
}
for (String s : list) {
System.out.println(s);
}
} catch (IOException e) {
System.out.println(e.getMessage());
System.exit(1);
}
}
After looking at the answers posted by my fellow Stack Overflow members I figured out that there was a very simple way of solving this issue and that was by using Scanner rather than using BufferedReader. I am not sure why I didn't think of this before, but hindsight is 2020. Anyway, the code below is what I used to solve my issue.
public static void main(String[] args) {
ArrayList<String> test = new ArrayList<>();
File file = new File("test.txt");
try {
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
test.add(sc.next()); // The id
test.add(sc.next()); // The name
}
sc.close();
System.out.println(test.toString());
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
All this is doing is getting each line with the different data on it and is skipping the blank. From there it is adding it to an ArrayList for later processing. Remember K.I.S.S (Keep It Simple Stupid) no need to overcomplicate anything.
Related
I am trying to setup a highscore system to sort the scores from a file and seperate the names from the numbers. But when I try to use readline twice it skips 1 line because of the other readline method. Can somebody help me please, it's for school!
Example of the file:
kevin:50 dustin:31 nobody:71 imax:23
Here is the code:
public class Main {
public static void main(String[] args) {
ArrayList<Integer> result = new ArrayList<>();
String name="";
try (BufferedReader br= new BufferedReader(new FileReader("res/highscore.txt"))){
while (br.ready()){
result.add(Integer.parseInt(br.readLine().split(":")[1]));
name = br.readLine().split(";")[0];
System.out.println(name);
}
Collections.sort(result);
Collections.reverse(result);
for (Integer integer : result) {
System.out.println(integer);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
A bit of explanation on #thewho69's answer.
You have fallen into the trap of side-effects. A method might not only do what its name would intuitively suggest. In this example, the readLine() method does not only read the upcoming line, but also sets the cursor position to the beginning of the next line.
This makes the readLine method not idempotent, which means that calling the method twice with the same parameters (in this case none) will not necessarily return the same output.
In order not to fall into this trap, you have to find a way to use the current one line multiple times, while calling the br.readLine() method only once - thus setting the cursor position only once in an iteration, which is desirable in this case. A good solution to this problem is what #thewho69 suggested ~20mins ago.
Simply store each line in a variable:
public class Main {
public static void main(String[] args) {
ArrayList<Integer> result = new ArrayList<>();
String name="";
try (BufferedReader br= new BufferedReader(new FileReader("res/highscore.txt"))){
String line;
while ((line = br.readLine()) != null){
result.add(Integer.parseInt(line.split(":")[1]));
name = line.split(";")[0];
System.out.println(name);
}
Collections.sort(result);
Collections.reverse(result);
for (Integer integer : result) {
System.out.println(integer);
}
} catch (IOException e) {
e.printStackTrace();
}
}
Problem: I can't parse my file test.txt, by spaces. I can 1) read text files, and I can 2) parse strings, but I cannot connect the two and parse a text file! My purpose is to learn how to analyze text files. This is a simplified approach to that.
Progress: Thus far, I can read test.txt using FileReader and BufferedReader, and print it to console. Further, I can parse simple String variables. The individual operations run, but I'm struggling with parsing an actual text file. I believe this is because my test.txt is stored in the buffer, and after I .close() it, I can't print it.
Text File Content:
This is a
text file created, only
for testing purposes.
Code:
import java.io.*;
public class ReadFile {
//create method to split text file, call this from main
public void splitIt(String toTest)
{
String[] result = toTest.split(" ");
for (String piece:result)
{
//loop through the array and print each piece
System.out.print(piece);
}
}
public static void main(String[] args) {
//create readfile method
try
{
File test = new File("C:\\final\\test.txt");
FileReader fileReader = new FileReader(test);
BufferedReader reader = new BufferedReader(fileReader);
String line = null;
//While there are still lines to be read, read and print them
while((line = reader.readLine()) != null)
{
System.out.println(line);
splitIt(line);
}
reader.close();
}
//Catch those errors!
catch (Exception ex)
{
ex.printStackTrace();
}
// readFileMethod a = new readFileMethod(line);
System.out.println(a.splitIt());
}
}
Preemptive thank you for your sharing your knowledge. Many posts on reading and parsing have been solved here on SO, but I've not the understanding to implement others' solutions. Please excuse me, I've only been learning Java a few months and still struggle with the basics.
Ok lets make the splitting into a mthod
private static void splitIt (String toTest) {
String[] result = toTest.split(" ");
for (String piece:result)
{
//loop through the array and print each piece.
System.out.println(piece);
}
}
then you can call it from within
while((line = reader.readLine()) != null)
{
System.out.println(line);
splitIt (line);
}
Building on Scary Wombat and your code, i made some changes.
It should now print the Line that is being read in and each word that is separated by space.
import java.io.*;
public class ReadFile {
//create method to split text file, call this from main
public static void splitIt(String toTest)
{
String[] result = toTest.split(" ");
for (String piece:result)
{
//loop through the array and print each piece
System.out.println(piece);
}
}
public static void main(String[] args) {
//create readfile method
try
{
File test = new File("C:\\final\\test.txt");
FileReader fileReader = new FileReader(test);
BufferedReader reader = new BufferedReader(fileReader);
String line = null;
//While there are still lines to be read, read and print them
while((line = reader.readLine()) != null)
{
System.out.println(line); // print the current line
splitIt(line);
}
reader.close();
}
//Catch those errors!
catch (Exception ex)
{
ex.printStackTrace();
}
}
}
I have to make an EPG app using java, but I am kind of new in programming and it's due tomorrow and it's still not working properly.
I have a question about a small part: I have to read the programs from a text file. Each line contains multiple things, the channel, the title of the program, a subtitle, a category, etcetera.
I have to make sure that I can read the separate parts of each line, but it's not really working, it's only printing the parts from the first line.
I am trying, but I can't find why it's not printing all the parts from all the lines in stead of printing only the parts from the first line. Here's the code:
BufferedReader reader = new BufferedReader(newFileReader(filepath));
while (true) {
String line = reader.readLine();
if (line == null) {
break;
}
}
String[] parts = line.split("\\|", -1);
for(int i = 0; i < parts.length; i++) {
System.out.println(parts[i]);
}
reader.close();
Does anybody know how to get all the lines in stead of only the first?
Thank you!
readLine() only reads one line, so you need to loop it, as you said.
BUT with reading to the String inside of the while loop you always overwrite that String.
You would need to declare the String above the while loop that you can access it from outside, too.
BTW, it seems that your braces for the if don't match.
Anyway, I'd fill the information into an ArrayList, look below:
List<String> list = new ArrayList<>();
String content;
// readLine() and close() may throw errors, so they require you to catch it…
try {
while ((content = reader.readLine()) != null) {
list.add(content);
}
reader.close();
} catch (IOException e) {
// This just prints the error log to the console if something goes wrong
e.printStackTrace();
}
// Now proceed with your list, e.g. retrieve first item and split
String[] parts = list.get(0).split("\\|", -1);
// You can simplify the for loop like this,
// you call this for each:
for (String s : parts) {
System.out.println(s);
}
Use apache commons lib
File file = new File("test.txt");
List<String> lines = FileUtils.readLines(file);
As ArrayList is Dynamic,try,
private static List<String> readFile(String filepath) {
String line = null;
List<String> list = new ArrayList<String>();
try {
BufferedReader reader = new BufferedReader(new FileReader(filepath));
while((line = reader.readLine()) != null){
list.add(line);
}
} catch (Exception e) {
e.printStackTrace();
}
return list;
}
Sample data in csv file
##Troubleshooting DHCP Configuration
#Module 3: Point-to-Point Protocol (PPP)
##Configuring HDLC Encapsulation
Hardware is HD64570
So i want to get the lines as
#Troubleshooting DHCP Configuratin
Module 3: Point-to-Point Protocol(PPP)
#Configuring HDLC Encapsulation
Hardware is HD64570
I have written sample code
public class ReadCSV {
public static BufferedReader br = null;
public static void main(String[] args) {
ReadCSV obj = new ReadCSV();
obj.run();
}
public void run() {
String sCurrentLine;
try {
br = new BufferedReader(new FileReader("D:\\compare\\Genre_Subgenre.csv"));
try {
while ((sCurrentLine = br.readLine()) != null) {
if(sCurrentLine.charAt(0) == '#'){
System.out.println(sCurrentLine);
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
I am getting below error
##Troubleshooting DHCP Configuration
#Module 3: Point-to-Point Protocol (PPP)
##Configuring HDLC Encapsulation
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0
at java.lang.String.charAt(Unknown Source)
at example.ReadCSV.main(ReadCSV.java:19)
Please suggest me how to do this?
Steps:
Read the CSV file line by line
Use line.replaceFirst("#", "") to remove the first # from each line
Write the modified lines to an output stream (file or String) which suites you
If the variable s contains the content of the CSV file as String
s = s.replace("##", "#");
will replace all the occurrencies of '##" with '#'
You need something like String line=buffer.readLine()
Check the first character of the line with line.charAt(0)=='#'
Get the new String with String newLine=line.substring(1)
This is a rather trivial question. Rather than do the work for you, I'll outline the steps that you need to take without gifting you the answer.
Read in a file line by line
Take the first line and check if the first character of this line is a # - If it is, create a substring of this line excluding the first character ( or use fileLine.replaceFirst("#", ""); )
Store this line somewhere in an array like data structure or simply replace the current variable with the edited one ( fileLine = fileLine.replaceFirst("#", ""); )
Repeat until no more lines left from file.
If you want to add these changes to the file, simply overwrite the old file with the new lines (e.g. Using a steam reader and setting second parameter to false would overwrite)
Make an attempt and show us what you have tried, people will be more likely to help if they believe you have attempted the problem yourself thoroughly first.
package stackoverflow.q_25054783;
import java.util.Arrays;
public class RemoveHash {
public static void main(String[] args) {
String [] strArray = new String [3];
strArray[0] = "##Troubleshooting DHCP Configuration";
strArray[1] = "#Module 3: Point-to-Point Protocol (PPP)";
strArray[2] = "##Configuring HDLC Encapsulation";
System.out.println("Original array: " + Arrays.toString(strArray));
for (int i = 0; i < strArray.length; i++) {
strArray[i] = strArray[i].replaceFirst("#", "");
}
System.out.println("Updated array: " + Arrays.toString(strArray));
}
}
//Output:
//Original array: [##Troubleshooting DHCP Configuration, #Module 3: Point-to-Point Protocol (PPP), ##Configuring HDLC Encapsulation]
//Updated array: [#Troubleshooting DHCP Configuration, Module 3: Point-to-Point Protocol (PPP), #Configuring HDLC Encapsulation]
OpenCSV reads CSV file line by line and gives you an array of strings, where each string is one comma separated value, right? Thus, you are operating on a string.
You want to remove '#' symbol from the beginning of the string (if it is there). Correct?
Then this should do it:
CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
String [] nextLine;
while ((nextLine = reader.readNext()) != null) {
if (nextLine[0].charAt(0) == '#') {
nextLine[0] = nextLine[0].substring(1, nextLine[0].length());
}
}
Replacing the first '#' symbol on each of the lines in the CSV file.
private List<String> getFileContentWithoutFirstChar(File f){
try (BufferedReader input = new BufferedReader(new InputStreamReader(new FileInputStream(f), Charset.forName("UTF-8")))){
List<String> lines = new ArrayList<String>();
for(String line = input.readLine(); line != null; line = input.readLine()) {
lines.add(line.substring(1));
}
return lines
} catch(IOException e) {
e.printStackTrace();
System.exit(1);
return null;
}
}
private void writeFile(List<String> lines, File f){
try(BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(f), StandardCharsets.UTF_8))){
for(String line : lines){
bw.write(content);
}
bw.flush();
}catch (Exception e) {
e.printStackTrace();
}
}
main(){
File f = new File("file/path");
List<Stirng> lines = getFileContent(f);
f.delete();
writeFile(lines, f);
}
I am trying to write a java program to parse relevant strings from a .txt file with a certain format.
I want to use the contents of the .txt file to initiate data for my classes. A sample file would look like this:
Movies
Lord of the Rings: 180
Fight Club: 120
...
Theaters
A:100
B:50
C:200
...
Shows
1,1,960
1,1,1080
1,1,1200
1,3,1020
1,3,1140
2,2,990
2,2,1210
...
Prices
Adult:10
Child:7
Senior:8
...
End
This is what I have so far (and it is returning an error when trying to read the above file to initialize my class.
public static void inititializeFromFile(String fileName) throws IOException {
BufferedReader reader = new BufferedReader(new FileReader(fileName));
String line;
while((line = reader.readLine()) != null) {
if(line.equals("Movies")) {
while (!(line.equals("Theaters"))) {
String currentline = line;
String[] parts = currentline.split(":");
String part1 = parts[0];
String part2 = parts[1];
movies.add(new Movie(part1, part2));
}
}
// do basic string comparisons here
if(line.equals("...")) {
// do something
}
else if(line.contains(":")) {
// most likely of type A:100, B:50
}
else if(line.equals("End")) {
// do something
}
else {
// anything else
}
}
reader.close();
}
}
Here is a sample program that will read in the file for you, line by line, and has some scenarios to determine what type of line we are looking at. I was lazy and threw the IOExceptions that might be thrown at me in the code - you should never do this, instead modify the program to use a try catch.
import java.io.*;
public class tmp {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new FileReader("file.txt"));
String line;
while((line = br.readLine()) != null) {
// do basic string comparisons here
if(line.equals("...")) {
// do something
}
else if(line.contains(":")) {
// most likely of type A:100, B:50
}
else if(line.equals("End")) {
// do something
}
else {
// anything else
}
}
br.close();
}
}