Develop Reference

How to read the information from a txt file into an arraylist

I have a txt document where each line is an independent message. This may include name, date of birth, address, etc. In addition to the address, all other information is in a row. Their order is not fixed. Name and birthday must be available, other information may not be available. If there is no name or birthday, this person should be ignored. Different people use blank lines to distinguish them. I want to read this information and put them in the arraylist, but I have no idea how to write the code.
My initial idea was to use a loop to read the content and store it, and if there was a blank line, start saving another content. But how to implement the code specifically I have no idea.
public class InforProcessor {
private File recordFile;
private File instructionFile;
private File outputFile;
private InforList inforlist;
public InforProcessor(String[]s)
{
recordFile = new File(s[0]);
instructionFile = new File(s[1]);
outputFile = new File(s[2]);
inforlist = new InforList();
}
}
This is my existing code, I want to read the contents of the recordFile and write to the arraylist.
Input file is like：
name john
birthday 11-11-2015
Address 11 Harry St, montain, TRY
birthday 12-25-2017
name peter
Postcode 2005
name jane
birthday 25-19-1998
Address 25 jeoje St, Sky, FLY
Postcode 1998
name geoge
The output information or useful information should be:
name john
birthday 11-11-2015
Address 11 Harry St, montain, TRY
birthday 12-25-2017
name peter
Postcode 2005
name jane
birthday 25-19-1998
Address 25 jeoje St, Sky, FLY
The last information should be delete because it do not have birthday.

First,you need to read all line from file,and every message splited by empty line.
Second,iterate over the message and check the messag is valid or not,if the message is valid then add the message to list.
private static List<String> filterFile(final String input) throws Exception {
List<String> result = new ArrayList<>();
List<String> lines = FileUtils.readLines(new File(input), "UTF-8");
System.out.println(lines.size());
int begin = 0;
int end = 0;
for (; end < lines.size(); end++) {
if (Strings.isNullOrEmpty(lines.get(end))) {
if (isValidInfo(lines, begin, end)) {
result.addAll(lines.subList(begin, end + 1));
}
begin = end + 1;
}
}
return result;
}
if message has name and birthday,the message is we want.
private static boolean isValidInfo(List<String> infos, int begin, int end) {
int counts = 0;
for (int i = begin; i < end; i++) {
String line = infos.get(i);
if (line.startsWith("name")) {
counts++;
}
if (line.startsWith("birthday")) {
counts++;
}
}
return counts == 2;
}

Android read text file and store into variable based on first word

I am doing a reading text file practice where I read and store the data into a string array object. One ArrayList data should have photo, title, website, and date. The text file looks like this:
photo:android_pie
title:Android Pie: Everything you need to know about Android 9
website:https://www.androidcentral.com/pie
date:20-08-2018
photo:oppo
title:OPPO Find X display
website:https://www.androidpit.com/oppo-find-x-display-review
date:25-08-2018
photo:android_pie2
title:Android 9 Pie: What Are App Actions & How To Use Them
website:https://www.androidheadlines.com/2018/08/android-9-pie-what-are-app-
actions-how-to-use-them.html
date:16-09-2018
I am trying to split and store them into a string array, which is an instance of my object class:
private List<ItemObjects> itemList;
and this is the constructor of my object class:
public ItemObjects(String photo, String name, String link, String date) {
this.photo = photo;
this.name = name;
this.link = link;
this.date = date;
}
I tried this but the ":" separator doesnt separate it like I want it to:
while ((sItems = bufferedReader.readLine()) != null) {
if (!sItems.equals("")) {
String[] tmpItemArr = sItems.split("\\:");
listViewItems.add(new ItemObjects(tmpItemArr[0], tmpItemArr[1], tmpItemArr[2], tmpItemArr[3]));
}
}
What is the best way of doing this? I have tried using for loop which stops at third line and adds the next one as new data. There are several online ways of doing it but some are very complicated and I am having trouble understanding it.

The problem is your understanding of using both the split function and the BufferReader.
By using readline function you are reading only one line so your split will split the first line only, you need to read the 4 first lines then add the item.
int count = 0;
String[] tmpItemArr = new String[4];
while ((sItems = bufferedReader.readLine()) != null) {
if (!sItems.equals("")) {
tmpItemArr[count] = sItems.split(":")[1];
count++;
if (count > 3) {
listViewItems.add(new ItemObjects(tmpItemArr[0], tmpItemArr[1], tmpItemArr[2], tmpItemArr[3]));
count = 0;
}
}
}

NullPointerException when setting variables to objects in ArrayList

I have an ArrayList containing Movie objects which I produced from a List containing File objects using this method:
// returns a list containing movie objects with correct names
private static ArrayList<Movie> createMovieObjs(Collection<File> videoFiles) {
ArrayList<Movie> movieArrayList = new ArrayList<>();
Matcher matcher;
for (File file : videoFiles) {
matcher = Movie.NAME_PATTERN.matcher(file.getName());
while (matcher.find()) {
String movieName = matcher.group(1).replaceAll("\\.", " ");
Movie movie = new Movie(movieName);
if (!movieArrayList.contains(movie)) {
movieArrayList.add(movie);
}
}
}
return movieArrayList;
}
Everything works fine in above code, getting correct ArrayList.
Then I want to parse info for each Movie object in this ArrayList and set that info to that Movie object:
// want to parse genre, release year and imdbrating for every Movie object
for (Movie movie : movieArrayList) {
try {
movie.imdbParser();
} catch (IOException e) {
System.out.println("Parsing failed: " + e);
}
}
Here is Movie.imdbParser which uses Movie.createXmlLink (createXmlLink works fine on its own, so thas imdbParser - tested both):
private String createXmlLink() {
StringBuilder sb = new StringBuilder(XML_PART_ONE);
// need to replace spaces in movie names to "+" - api works that way
String namePassedToXml = this.title.replaceAll(" ", "+");
sb.append(namePassedToXml);
sb.append(XML_PART_TWO);
return sb.toString();
}
// parses IMDB page and sets releaseDate, genre and imdbRating in Movie objects
public void imdbParser() throws IOException {
String xmlLink = createXmlLink();
// using "new Url..." because my xml is on the web, not on my disk
Document doc = Jsoup.parse(new URL(xmlLink).openStream(), "UTF-8", "", Parser.xmlParser());
Element movieFromXml = doc.select("movie").first();
// using array to extract only last genre name - usually the most substantive one
String[] genreArray = movieFromXml.attr("genre").split(", ");
this.genre = genreArray[genreArray.length - 1];
this.imdbRating = Float.parseFloat(movieFromXml.attr("imdbRating"));
// using array to extract only year of release
String[] dateArray = movieFromXml.attr("released").split(" ");
this.releaseYear = Integer.parseInt(dateArray[2]);
}
Problems seems to be with accessing Movie objects, it doesn't create good XMLLink so when it tries to access genre in XML it throws NPE.
My error:
Exception in thread "main" java.lang.NullPointerException
at com.michal.Movie.imdbParser(Movie.java:79)
at com.michal.Main.main(Main.java:52)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Movie.java:79 is:
String[] genreArray = movieFromXml.attr("genre").split(", ");
and Main.java:52 is:
movie.imdbParser();

A lot of errors such as this are caused by the data not being as you expect. Often when dealing with a lot of data then sometimes it can be just a single record that does not "conform"!
You say that this line is causing you problems;
String[] genreArray = movieFromXml.attr("genre").split(", ");
So split the line down and debug your application to find the issue. If you can't debug then export the results to a log file.
Check that movieFromXml is not NULL.
Check that movieFromXml contains a "genre" attribute as you expect
Check that the data in the attribute can be split as you expect, and produces a valid output.
Often, it is good to view the data being retrieved prior to this call. I often find it useful to dump the data out to file and then load it in an external viewer to check that it is how I expect.

When you make a chain of calling method like this: movieFromXml.attr("genre").split(", "), you have to make sure that each of the preceding element is not null. In this case, you have to make sure that movieFromXml is not null and movieFromXml.attr("genre") is not null.

How to replace words with Parallel arrays

Hello i am new to this forum. I am fairly new to Java. I am trying to convert USA to UK words so that when i input a sentence containing any of the USA words, the output will be will be the sentence but replaced with UK words. This is my attempt:
import javax.swing.JOptionPane;
public class PArraystest
{
public static void main(String [] arg)
{
String[] wordUSA = {"Cell", "Elevator", "Fries", "Gasoline", "Faucet"};
String[] wordUK = {"Mobile", "Lift", "Chips", "Petrol", "Tap"};
String changeUK = "";
String sent;
sent = JOptionPane.showInputDialog("What name do you want to search for?");
for (int i = 0; i < wordUSA.length; i++)
{
if (sent.contains(wordUSA[i]))
{
sent.replace((wordUK)[i],(wordUSA)[i]);
//break;
}
}
//if (changeUK.equals(""))
//System.out.println(" was not found.");
//else
System.out.println(sent);
}
}

Two things:
You need to use assign the string returned from replace to sent again, or sent will be unchanged`.
The replace method is public String replace(char oldChar, char newChar), so the oldChar US word should come first, followed by the UK word.
This is the correct line: sent = sent.replace(wordUSA[i],wordUK[i]);

The replace method returns a new String with the replaced text:
//sent.replace((wordUK)[i],(wordUSA)[i]);
sent = sent.replace((wordUK)[i],(wordUSA)[i]);

Two problems:
First, you should assign the replaced string back to sent.
Second, you should use replaceAll instead of replace.

There's a whole framework of functionality devoted to this in Java called internationalizaion (i18n)
While the sample below is primarily for generation origianlly I thought I'd point it out because you could probably devise how to run it in reverse as well.
Here's a snippet that shows the proper way to go about this:
http://docs.oracle.com/javase/tutorial/i18n/intro/after.html
(all code below is theirs and not my own)
Note that to run this you'll need the resource files from the site or the versions I have provided below from the site
import java.util.*;
public class I18NSample {
static public void main(String[] args) {
String language;
String country;
if (args.length != 2) {
language = new String("en");
country = new String("US");
} else {
language = new String(args[0]);
country = new String(args[1]);
}
Locale currentLocale;
ResourceBundle messages;
currentLocale = new Locale(language, country);
messages = ResourceBundle.getBundle("MessagesBundle", currentLocale);
System.out.println(messages.getString("greetings"));
System.out.println(messages.getString("inquiry"));
System.out.println(messages.getString("farewell"));
}
}
MessagesBundle.properties:
greetings = Hello.
farewell = Goodbye.
inquiry = How are you?
MessagesBundle_en_US.properties:
greetings = Hello.
farewell = Goodbye.
inquiry = How are you?
MessagesBundle_fr_FR.properties:
greetings = Bonjour.
farewell = Au revoir.
inquiry = Comment allez-vous?

Extracting data from a collection in Java

I have a csv dataset like this:
A, 10, USA
B,30, UK
C,4,IT
A,20,UK
B,10,USA
I want to read this csv lines and provide the following output:
A has ran 30 miles with average of 15.
B has ran 30 miles with average of 20.
C has ran 4 miles with average of 4.
I want to achieve this in Java. I have done this in C# by using Linq:
var readlines = File.ReadAllLines(filename);
var query = from lines in readlines
let data = lines.Split(',')
select new
{
Name = data[0],
Miles = data[1],
};
var values = query.GroupBy(x => new {x.Name}).Select(group => new { Person = group.Key, Events = group.Sum(g =>Convert.ToDouble(g.Miles)) ,Count = group.Count() });
I am looking to do this in Java, and I am not sure if I can do this without using any third party library or not? Any ideas?
So far, my code looks like this in Java:
CSVReader reader = new CSVReader(new FileReader(filename));
java.util.List<String[]> content = reader.readAll();
String[] row = null;
for(Object object:content)
{
row = (String[]) object;
String Name = row[0];
String Miles = row[1];
System.out.printf("%s has ran %s miles %n",Name,Miles);
}
reader.close();
}
I am looking for a nice way to get the total milage value for each name to calculate for the average.

As a C# developer, it is hard sometimes not to miss the features of linq. But as Farlan suggested you could do something like this:
CSVReader reader = new CSVReader(new FileReader(filename));
java.util.List<String[]> content = reader.readAll();
Map<String, Group> groups = new HashMap<>();
for(String[] row : content)
{
String Name = row[0];
String Miles = row[1];
System.out.printf("%s has ran %s miles %n", Name, Miles);
if (groups.containsKey(Name)){
groups.get(Name).Add(Double.valueOf(Miles));
} else {
Group g = new Group();
g.Add(Double.valueOf(Miles));
groups.put(Name, g);
}
}
reader.close();
for (String name : groups.keySet())
{
System.out.println(name + " ran " + groups.get(name).total() + " with avg of " + groups.get(name).average());
}
}
class Group {
private List<Double> miles;
public Group()
{
miles = new ArrayList<>();
}
public Double total(){
double sum = 0;
for (Double mile : miles)
{
sum += mile;
}
return sum;
}
public Double average(){
if (miles.size() == 0)
return 0d;
return total() / miles.size();
}
public void Add(Double m){
miles.add(m);
}
}

Use Java's BufferedReader class:
BufferedReader in = new BufferedReader(new FileReader("your.csv"));
String line;
while ( (line = in.readLine()) != null) {
String [] fields = line.split(",");
System.out.println(fields[0] + " has ran " + fields[1] + " miles with average " + fields[2]);
}

There are quite a few ways to do this, some long-winded approaches, some shorter. The issue is that Java can be very verbose for doing simple tasks, so the better approaches can be a bit uglier.
The example below shows you exactly how to achieve this, par the printing. Bear in mind however, it might not be the best approach but I feel its more of the easier ones to read and comprehend.
final File csvFile = new File("filename.csv");
final Scanner reader = new Scanner(csvFile);
final Map<String, Integer> info = new HashMap<>(); //Store the data
//Until there is are no more lines, continue
while (reader.hasNextLine()) {
final String[] data = reader.nextLine().split(","); // data[0] = A. [1] = 10. [2] = USA
final String alpha = data[0];
if (!info.containsKey(alpha)) {
info.put(alpha, Integer.parseInt(data[1]));
} else {
int miles = info.get(alpha);
info.put(alpha, miles + Integer.parseInt(data[1]));
}
}
reader.close();
The steps involved are simple:
Step 1 - Read the file.
By passing a File into the Scanner object, you set the target parsing to the File and not the console. Using the very neat hasNextLine() method, you can continually read each line until no more exist. Each line is then split by a comma, and stored in a String array for reference.
Step 2 - Associating the data.
As you want to cumulatively add the integers together, you need a way to associate already passed in letters with the numbers. A heavyweight but clean way of doing this is to use a HashMap. The Key which it takes is going to be a String, specifically A B or C. By taking advantage of the fact the Key is unique, we can use the O(1) containsKey(String) method to check if we've already read in the letter. If its new, add it to the HashMap and save the number with it. If however, the letter has been seen before, we find the old value, add it with the new one and overwrite the data inside the HashMap.
All you need to do now is print out the data. Feel free to take a different approach, but I hope this is a clear example of how you CAN do it in Java.

Maybe you could try this Java library: https://code.google.com/p/qood/
It handles data without any getter/setters, so it's more flexible than LINQ.
in your case, file "D:/input.csv" has 3 columns:
NAME,MILES,COUNTRY
A, 10, USA
B,30, UK
C,4,IT
A,20,UK
B,10,USA
the query code would be:
final QModel raw = QNew.modelCSV("D:/input.csv")
.debug(-1);//print out what read from CSV
raw.query()
.selectAs("OUTPUT",
"CONCAT(NAME,' has ran ',SUM(MILES),' miles with average of ',MEAN(MILES),'.')")
.groupBy("NAME")
.result().debug(-1)//print out the result
.to().fileCSV("D:/output.csv", "UTF-8");//write to another CSV file