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Is there a way loop through 2 arrays and print the element of array 1 if it contains the substring of any element from array 2?

The problem I am trying to solve is how to read lines from a text file and add it to an array. Then sort each element from this new array by the date that is also in each element. I will explain so its easier to understand but will explain what I am doing.
My text file (First column is name, second is Date of birth and last is the date the person died):
sarah jones,1966-12-02,2018-12-04
matt smith,1983-02-03,2020-03-02
john smith,1967-03-04,2017-04-04
I want to sort this file and output it to another file (testing by printing to console at the moment) by sorting it by the date the person died. A way I thought of doing this is to read each line and pass it to an array. Then read each element within the array, split it and then save the date the person died to another array. Then sort the array that has the death dates, loop through both arrays by seeing if the first element of the death date array matches the first element of the first line in the text file, if so then write it to another file. If not then go to the next line.
For example
BufferedReader reader = new BufferedReader(new FileReader("input_text.txt"));
PrintWriter outputStream = new PrintWriter(new FileWriter("output.txt",true));
ArrayList<String> lines = new ArrayList<String>();
ArrayList<String> substr_date = new ArrayList<String>();
String currentline = reader.readLine();
while(currentline !=null){
String a_line[] = currentline.split(",");
substr_date.add(a_line[2])
lines.add(currentline);
currentline = reader.readLine();
}
Collections.sort(substr_date);
for(String date : substr_date){
for(String line : lines){
if(line.contains(date)){
System.out.println(line);
}
}
}
I expect the output to be:
john smith,1967-03-04,2017-04-04
sarah jones,1966-12-02,2018-12-04
matt smith,1983-02-03,2020-03-02
The results are initially in order but then some lines are repeated multiple times and then the whole text file in repeated to the console and becomes a mess. I am not sure how to go about doing this. I am new to java and not sure if I asked this question properly either so if you need any more info please ask.

I would create class for objects which you can insert into a list and then define a comparator on this class which you can use to sort.
Here is an example of the class you could define:
static class DeceasedPerson {
String name;
LocalDate birthDate;
LocalDate deathDate;
DeceasedPerson(String name, LocalDate birthDate, LocalDate deathDate) {
this.name = name;
this.birthDate = birthDate;
this.deathDate = deathDate;
}
#Override
public String toString() {
return name + ", " + birthDate + ", " + deathDate;
}
}
Then you could simply load objects based on this class into a list which you sort using a comparator. Here is some sample code you can run with the class defined above:
public static void main(String[] args) {
String input =
"matt smith,1983-02-03,2020-03-02\n" +
"sarah jones,1966-12-02,2018-12-04\n" +
"john smith,1967-03-04,2017-04-04\n";
List<DeceasedPerson> deceasedPersonList = new ArrayList<>();
try (Scanner scanner = new Scanner(input)) {
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
String[] array = line.split(",");
DeceasedPerson deceasedPerson = new DeceasedPerson(array[0],
LocalDate.parse(array[1]), LocalDate.parse(array[2]));
deceasedPersonList.add(deceasedPerson);
}
}
deceasedPersonList.sort(Comparator.comparing(o -> o.deathDate));
deceasedPersonList.forEach(System.out::println);
}
If you run the code above using the DeceasedPerson class you should see on the console the following output:
john smith, 1967-03-04, 2017-04-04
sarah jones, 1966-12-02, 2018-12-04
matt smith, 1983-02-03, 2020-03-02
You could actually also use a TreeSet instead of a List in the main method above and achieve the same results. Here is a move concise alternative:
public static void main(String[] args) {
String input =
"matt smith,1983-02-03,2020-03-02\n" +
"sarah jones,1966-12-02,2018-12-04\n" +
"john smith,1967-03-04,2017-04-04\n";
Set<DeceasedPerson> deceasedPersonList = new TreeSet<>(Comparator.comparing(o -> o.deathDate));
try (Scanner scanner = new Scanner(input)) {
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
String[] array = line.split(",");
DeceasedPerson deceasedPerson = new DeceasedPerson(array[0],
LocalDate.parse(array[1]), LocalDate.parse(array[2]));
deceasedPersonList.add(deceasedPerson);
}
}
deceasedPersonList.forEach(System.out::println);
}

The way you are doing is a long shot. You can do this in much simpler way. You could pass a comparator to the Collections.sort() method like this.
Collections.sort(substr_date, new Comparator<String>{
#Override
public int compare(String str1, String str2){
String dd1 = str1.split(",")[2];
String dd2 = str2.split(",")[2];
return dd1.compareTo(dd2);
}
});
Comparing dates like this, though, is not a good approach. You should convert the date string to LocalDateTime and then use isBefore() or isAfter() to compare them. For ex,
public int compare(String str1, String str2){
DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd")
LocalDateTime d1 = LocalDateTime.parse(str1.split(",")[2],format);
LocalDateTime d2 = LocalDateTime.parse(str2.split(",")[2],format);
return d1.isBefore(d2)?-1:(d1.isAfter(d2)?1:0);
}

Compare array to text file

I have a text file: "example.csv" that contains 1000's of rows
The text file contains
Dog, 3123
Cat, 6544
Chicken, 8943
And another: "example2.csv" that contains 1000's of rows
Fruit, 3243
Banana, 9432
Chicken, 2043
And an array that contains (100's of rows):
Home, Dan, Dog, 4234
Home, Bug, Chicken, 3213
Home, Hds, Banana, 4324
Out, Bgh, Poodle, 3129
I need to change the third column in the array to the value found in the CSV, example.csv. If it is not found in the first one, it needs to look in the second one, example2.csv.
As you can see in my example, Chicken appears in both, but it needs to find the value from example.csv. However, Fruit only appears in the second, so it needs to find the value from example2.csv.
Anything not found in either csv needs to displayed that it does not exist.
Any example being:
Home, Dan, Dog, 4234
Home, Bug, Chicken, 3213
Out, Bgh, Poodle, 3129
BECOMES
Home, Dan, 3123, 4234
Home, Bug, 8943, 3213
Home, Hds, 9432, 4324
Out, Bgh, Poodle, 3129 : Display :Missing - Poodle
Thank you!
Number is the array and isFound starts off as false
Split by is: ","
Here is my attempt:
try {
//Scanner inFile = new Scanner (new FileReader("Files\\"+"ABTutor2018Sem2"+".csv")); // import file
brStudents = new BufferedReader(new FileReader("Files\\deploystudio.csv"));
brStudents2 = new BufferedReader(new FileReader("Files\\deploystudio2.csv"));
while ((line = brStudents.readLine()) != null) {
arrSubjectsDeploy = line.split(splitBy);
isFound = false;
for(int h = 0; h < l; h++) {
arrSubjects = Number[h].split(splitBy);
line2 = "";
errorMessage = arrSubjectsDeploy[0];
if(arrSubjects[2].equals(arrSubjectsDeploy[0])) {
arrSubjects[2] = arrSubjectsDeploy[1];
m++;
tempHolder = "";
isFound = true;
}
if(h == l-1 && isFound == false) {
System.out.println("Missing: " + errorMessage);
}
}
}
}
This is only trying to do the first text file ... but still does not work because it's looking at the contents of the textfile and seeing if it compares to the array, rather the the other way around.

You can use Map<String,String> to store contents of example.csv and example2.csv. Then iterate over your input array to check if it exists in either file.
Map<String, String> firstFile = readFileAndConvert("Files\\deploystudio.csv");
Map<String, String> secondFile = readFileAndConvert("Files\\deploystudio2.csv");
int index = 2;
String[][] finalArray =
{{"Home", "Dan", "Dog", "4234"}, {"Home", "Bug", "Chicken", "3213"},
{"Home", " Hds", "Banana", "4324"}, {"Out", " Bgh", "Poodle", "3129"}};
for(String[] row : finalArray) {
String valueToFind = row[index];
if(firstFile.containsKey(valueToFind)) {
row[index] = firstFile.get(valueToFind);
} else if(secondFile.containsKey(valueToFind)) {
row[index] = secondFile.get(valueToFind);
} else {
System.out.println("Missing " + valueToFind);
}
}
readFileAndConvert function using java 8. But you can achieve similar functionality with any other version too.
private Map<String, String> readFileAndConvert(String path) throws IOException {
String SEPARATOR = ",";
try (Stream<String> lines = Files.lines(Paths.get(path))) {
return lines.map(line -> line.split(SEPARATOR))
.collect(Collectors.toMap(array -> array[0], array -> array[1]));
}
}

How to select random text value from specific row using java

I have three input fields.
First Name
Last item
Date Of Birth
I would like to get random data for each input from a property file.
This is how the property file looks. Field name and = should be ignored.
- First Name= Robert, Brian, Shawn, Bay, John, Paul
- Last Name= Jerry, Adam ,Lu , Eric
- Date of Birth= 01/12/12,12/10/12,1/2/17
Example: For First Name: File should randomly select one name from the following names
Robert, Brian, Shawn, Bay, John, Paul
Also I need to ignore anything before =
FileInputStream objfile = new FileInputStream(System.getProperty("user.dir "+path);
in = new BufferedReader(new InputStreamReader(objfile ));
String line = in.readLine();
while (line != null && !line.trim().isEmpty()) {
String eachRecord[]=line.trim().split(",");
Random rand = new Random();
//I need to pick first name randomly from the file from row 1.
send(firstName,(eachRecord[0]));

If you know that you're always going to have just those 3 lines in your property file I would get put each into a map with an index as the key then randomly generate a key in the range of the map.
// your code here to read the file in
HashMap<String, String> firstNameMap = new HashMap<String, String>();
HashMap<String, String> lastNameMap = new HashMap<String, String>();
HashMap<String, String> dobMap = new HashMap<String, String>();
String line;
while (line = in.readLine() != null) {
String[] parts = line.split("=");
if(parts[0].equals("First Name")) {
String[] values = lineParts[1].split(",");
for (int i = 0; i < values.length; ++i) {
firstNameMap.put(i, values[i]);
}
}
else if(parts[0].equals("Last Name")) {
// do the same as FN but for lastnamemap
}
else if(parts[0].equals("Date of Birth") {
// do the same as FN but for dobmap
}
}
// Now you can use the length of the map and a random number to get a value
// first name for instance:
int randomNum = ThreadLocalRandom.current().nextInt(0, firstNameMap.size(0 + 1);
System.out.println("First Name: " + firstNameMap.get(randomNum));
// and you would do the same for the other fields
The code can easily be refactored with some helper methods to make it cleaner, we'll leave that as a HW assignment :)
This way you have a cache of all your values that you can call at anytime and get a random value. I realize this isn't the most optimum solution having nested loops and 3 different maps but if your input file only contains 3 lines and you're not expecting to have millions of inputs it should be just fine.

Haven't programmed stuff like this in a long time.
Feel free to test it, and let me know if it works.
The result of this code should be a HashMap object called values
You can then get the specific fields you want from it, using get(field_name)
For example - values.get("First Name"). Make sure to use to correct case, because "first name" won't work.
If you want it all to be lower case, you can just add .toLowerCase() at the end of the line that puts the field and value into the HashMap
import java.lang.Math;
import java.util.HashMap;
public class Test
{
// arguments are passed using the text field below this editor
public static void main(String[] args)
{
// set the value of "in" here, so you actually read from it
HashMap<String, String> values = new HashMap<String, String>();
String line;
while (((line = in.readLine()) != null) && !line.trim().isEmpty()) {
if(!line.contains("=")) {
continue;
}
String[] lineParts = line.split("=");
String[] eachRecord = lineParts[1].split(",");
System.out.println("adding value of field type = " + lineParts[0].trim());
// now add the mapping to the values HashMap - values[field_name] = random_field_value
values.put(lineParts[0].trim(), eachRecord[(int) (Math.random() * eachRecord.length)].trim());
}
System.out.println("First Name = " + values.get("First Name"));
System.out.println("Last Name = " + values.get("Last Name"));
System.out.println("Date of Birth = " + values.get("Date of Birth"));
}
}

how to store file contents if match a condition

I have many albums in txt file and i want to read each line in the file while i read. I should check if the line start with Uppercase letter. So that means I should create new object of type Album, and if the line star with "0" that means is track and I should create new object of type Track and so on for an e.g of album which i want tack it from the file and store it in my java program:
Pink Floyd : Dark Side of the Moon
0:01:30 - Speak to me
0:06:48 - Brain Damage
.
.
etc.
And this is my code the file have 13 albums and each has many tracks with the period of every track.
if(Character.isUpperCase(line.charAt(0))==true) {
String[] token=line.split(":");
artistName=token[0];
albumTitle=token[1];
}
else {
tracks.add(new Track(line));
count2++;
}
album = new Album(artistName,albumTitle,tracks);
albumCollection.add(album);
so how to let the program understand that the start of album's tracks and end and then pass the array list of track to album object.
Thank

Your question is a bit difficult to understand but, I give it a try and imagined the scenario. I assume that you have already created Album and Track classes and everything works. I assume that your albums file looks as follow:
Pink Floyd : Dark Side of the Moon
0:01:30 - Speak to me
0:06:48 - Brain Damage
Another artist: Album name
0:02:33 - Whatever
0:16:21 - Blah Blah
Third artist: Album name
0:02:33 - X
0:16:21 - Y
0:02:33 - Z
0:16:21 - A
What you have to do is start reading the file line by line, which I believe that you are doing somewhere in the code that we cannot see. For each line you have the following condition which is fine
//you don't need to add == true in the if condition
if (Character.isUpperCase(line.charAt(0))) {
//Album found
} else {
//Track found
}
Every time you read a line. If Album found then you initialize an Album object and store it its artist, title and an empty list of tracks. Every time a track if found, check if the Album object is not null (if not null then it is current album) and retrieve its track list, add the new track to it and set the track list back to the Album object.
I have written the following code, assuming you have majority of it which we cannot see in this question. Go through the code and you will understand how a line is read and how an object of Album is created, how tracks are created and stored in the album. To test the following solution, copy/paste it in file same as class name and execute it, make sure you have the album.txt file containing the album.
import java.util.List;
import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
class Track {
String track;
public Track(String track) {
this.track = track;
}
//overriding toString() method for Track class
public String toString() {
return track;
}
}
class Album {
String artistName;
String albumTitle;
List < Track > tracks = new ArrayList < Track > ();
//Album Constructor
public Album(String artistName, String albumTitle) {
this.artistName = artistName;
this.albumTitle = albumTitle;
}
public List < Track > getTracks() {
return tracks;
}
public void setTracks(List < Track > tracks) {
this.tracks = tracks;
}
//overriding the toString method for Album
public String toString() {
StringBuilder album = new StringBuilder();
album.append("Artist name: " + artistName + "\n");
album.append("\n Album title : " + albumTitle + "\n\n");
for (int i = 0; i < tracks.size(); i++) {
album.append("\n Track " + (i + 1) + ":" + tracks.get(i).toString());
}
return album.toString();
}
}
public class ReadAlbums {
public static void main(String[] args) {
List < Album > albumsCollection = new ArrayList < Album > ();
BufferedReader in = null;
try { in = new BufferedReader(new FileReader("albums.txt"));
String line;
List < Track > currentTracks = new ArrayList < Track > ();
Album album = null;
while ((line = in .readLine()) != null) {
//no need to put == true in the if condition
if (Character.isUpperCase(line.charAt(0))) {
//Album found
String[] token = line.split(":");
//If the not the first ever album then add the previous album to the collection
if (album != null) {
albumsCollection.add(album);
}
//new album object is created with artist name and album title
album = new Album(token[0], token[1]);
//new empty track list is added to the album object
album.setTracks(new ArrayList < Track > ());
} else {
//Track found
//retrieve the track from Album album
currentTracks = album.getTracks();
//Add the track to the list of tracks obtained from album
currentTracks.add(new Track(line));
//add the updated track list back to the album object
album.setTracks(currentTracks);
}
}
//add the last album in the album collections
if(album != null) {
albumsCollection.add(album);
}
//close the input stream
in.close();
} catch (IOException e) {}
System.out.println("albums : " + albums.toString());
}
}
You get the following output:
albums : [Artist name: Pink Floyd
Album title : Dark Side of the Moon
Track 1:0:01:30 - Speak to me
Track 2:0:06:48 - Brain Damage, Artist name: Another artist
Album title : This is the second album
Track 1:0:02:33 - Whatever
Track 2:0:16:21 - Blah Blah, Artist name: Third artist
Album title : This is the third album
Track 1:0:02:33 - X ]
To print the data read from file back in the same format. You need to to loop through albums and for each album retrieve the list of tracks and then print the track.
for(int i = 0; i < albumsCollection.size();i++) {
Album album = albumsCollection.get(i);
System.out.println(album.getArtistName() + ":" + album.getAlbumTitle());
List<Tracks> tracks = album.getTracks();
for(int j = 0; j < tracks.size(); j++) {
System.out.println(tracks[j].toString());
}
}

yes it like this.
The Dave Brubeck Quartet : Take Five
0:06:44 - Blue Rondo a la Turk
0:07:22 - Strange Meadow Lark
0:05:24 - Take Five
0:04:16 - Pick Up Sticks
Goldfrapp : Supernature
0:03:24 - Ooh La La
0:03:25 - Lovely 2 C U
0:04:41 - Ride a White Horse

If you really want to do it like this and if your file REALLY always has this exact structure, a quick and dirty solution would be this:
ArrayList<Track> tracks = new ArrayList<Track>();
ArrayList<Album> albumCollection = new ArrayList<Album>();
Album album;
String artistName;
String albumTitle;
String[] token;
BufferedReader br = new BufferedReader(new FileReader("albums.txt"));
try {
String line = br.readLine();
while (line != null) {
if(!Character.isDigit(line.charAt(0)) {
// there is a problem if your artist name starts with a "0" so add some more checks here
token = line.split(" : ");
artistName = token[0];
albumTitle = token[1];
if(!tracks.isEmpty()) {
album = new Album(artistName,albumTitle,tracks);
albumCollection.add(album);
tracks.clear();
}
}
else {
tracks.add(new Track(line))
}
line = br.readLine();
}
} finally {
br.close();
}
You said you want to print all tracks?!
for(Album alb : albumCollection) {
// I dont know about your implementation of the Album class but I assume:
System.out.println(alb.getTitle());
System.out.println("##TRACKS###");
ArrayList<Track> trs = alb.getTracks();
for(Track tr : trs) {
String trackName = tr.getTitle(); // I assume again..
System.out.println(trackName);
// .....
}
}

Reading a special txt file in java

What I want to do is read a text file that has humans and animals. It will compile but has an error when I try to run it. I think I need a for loop to read the stringtokenizer to decipher between the human and animal in the txt file so far this is my driver class.
txt file:
Morely,Robert,123 Anywhere Street,15396,4,234.56,2
Bubba,Bulldog,58,4-15-2010,6-14-2011
Lucy,Bulldog,49,4-15-2010,6-14-2011
Wilder,John,457 Somewhere Road,78214,3,124.53,1
Ralph,Cat,12,01-16-2011,04-21-2012
Miller,John,639 Green Glenn Drive,96258,5,0.00,3
Major,Lab,105,07-10-2012,06-13-2013
King,Collie,58,06-14-2012,10-05-2012
Pippy,cat,10,04-25-2015,04-25-2015
Jones,Sam,34 Franklin Apt B,47196,1,32.09,1
Gunther,Swiss Mountain Dog,125,10-10-2013,10-10-2013
Smith,Jack,935 Garrison Blvd,67125,4,364.00,4
Perry,Parrot,5,NA,3-13-2014
Jake,German Shepherd,86,11-14-2013,11-14-2013
Sweetie,tabby cat,15,12-15-2013,2-15-2015
Pete,boa,8,NA,3-15-2015
Source:
import java.util.Scanner;
import java.util.StringTokenizer;
import java.io.File;
import java.io.IOException;
/**
* This is my driver class that reads from a txt file to put into an array and uses the class refrences so it can use the menu and spit out
*
* #author ******
* #version 11/25/2015
*/
public class Driver
{
/**
* Constructor for objects of class Driver, what it does is read in the txt file gets the two class refrences and loops through to read through the whole file looking for string tokens to go to the next line
* and closes the file at the end also uses for loop to count number of string tokens to decipher between human and pets.
*/
public static void main(String[] args) throws IOException
{
Pet p;
Human h;
Scanner input;
char menu;
input = new Scanner(new File("clientdata.txt"));
int nBalance;
int id;
/**
* this while statement goes through each line looking for the string tokenizer ",". I want to count each "," to decipher between Human and Animal
*/
while(input.hasNext())
{
StringTokenizer st = new StringTokenizer(input.nextLine(), ",");
h = new Human();
h.setLastName(st.nextToken());
h.setFirstName(st.nextToken());
h.setAddress(st.nextToken());
h.setCiD(Integer.parseInt(st.nextToken()));
h.setVisits(Integer.parseInt(st.nextToken()));
h.setBalance(Double.parseDouble(st.nextToken()));
p = new Pet(st.nextToken(), st.nextToken(), Integer.parseInt(st.nextToken()), st.nextToken(), st.nextToken());
}
/**
* this is my seond while statement that loops the case switch statements and asks the user for client ID
*/
menu = 'Y';
while(menu == 'y' || menu == 'Y') {
System.out.print("\nChose one:\n A- client names and outstanding balance \n B- client's pets, name, type and date of last visit\n C-change the client's outstanding balance: ");
menu = input.next().charAt(0);
System.out.print("Enter client ID: ");
id = input.nextInt();
h = new Human();
if(id == h.getCiD())//if the id entered up top is equal to one of the id's in the txt file then it continues to the menu
{
p = new Pet();
switch(menu)
{ case 'A':
System.out.println("client name: " + h.getFirstName() + "outstanding balance: " + h.getBalance());
break;
case 'B':
System.out.println("pet's name: " + p.getName() + "type of pet: " + p.getTanimal() + "date of last visit: " + p.getLastVisit());
break;
case 'C':
System.out.println("what do you want to change the clients balances to?");
input.close();
}
}
else// if not then it goes to this If statement saying that the Client does not exist
{
System.out.println("Client does not exist.");
}
}
}
}

You have a number of issues you need to overcome...
For each line, you need to determine the type of data the line represents
You need some way to keep track of the data you've loaded (of the clients and their pets)
You need some way to associate each pet with it's owner
The first could be done in a number of ways, assuming we can change the data. You could make the first token meaningful (human, pet); you could use JSON or XML instead. But lets assume for the moment, you can't change the format.
The key difference between the two types of data is the number of tokens they contain, 7 for people, 5 for pets.
while (input.hasNext()) {
String text = input.nextLine();
String[] parts = text.split(",");
if (parts.length == 7) {
// Parse owner
} else if (parts.length == 5) {
// Parse pet
} // else invalid data
For the second problem you could use arrays, but you would need to know in advance the number of elements you will need, the number of people and for each person, the number of pets
Oddly enough, I just noticed that the last element is an int and seems to represent the number of pets!!
Morely,Robert,123 Anywhere Street,15396,4,234.56,2
------------^
But that doesn't help us for the owners.
For the owners, you could use a List of some kind and when ever you create a new Human, you would simply add them to the List, for example...
List<Human> humans = new ArrayList<>(25);
//...
if (parts.length == 7) {
// Parse the properties
human = new Human(...);
humans.add(human);
} else if (parts.length == 5) {
Thirdly, for the pets, each Pet should associated directly with the owner, for example:
Human human = null;
while (input.hasNext()) {
String text = input.nextLine();
String[] parts = text.split(",");
if (parts.length == 7) {
//...
} else if (parts.length == 5) {
if (human != null) {
// Parse pet properties
Pet pet = new Pet(name, type, age, date1, date2);
human.add(pet);
} else {
throw new NullPointerException("Found pet without human");
}
}
Okay, so all this does, is each time we create a Human, we keep a reference to the "current" or "last" owner created. For each "pet" line we parse, we add it to the owner.
Now, the Human class could use either a array or List to manage the pets, either will work, as we know the expected number of pets. You would then provide getters in the Human class to get a reference to the pets.
Because out-of-context code can be hard to read, this is an example of what you might be able to do...
Scanner input = new Scanner(new File("data.txt"));
List<Human> humans = new ArrayList<>(25);
Human human = null;
while (input.hasNext()) {
String text = input.nextLine();
String[] parts = text.split(",");
if (parts.length == 7) {
String firstName = parts[0];
String lastName = parts[1];
String address = parts[2];
int cid = Integer.parseInt(parts[3]);
int vists = Integer.parseInt(parts[4]);
double balance = Double.parseDouble(parts[5]);
int other = Integer.parseInt(parts[6]);
human = new Human(firstName, lastName, address, cid, vists, balance, other);
humans.add(human);
} else if (parts.length == 5) {
if (human != null) {
String name = parts[0];
String type = parts[1];
int age = Integer.parseInt(parts[2]);
String date1 = parts[3];
String date2 = parts[4];
Pet pet = new Pet(name, type, age, date1, date2);
human.add(pet);
} else {
throw new NullPointerException("Found pet without human");
}
}
}

What about using split() function instead of using StringTokenizer?
Say, You can change your first while loop like below:
while (input.hasNext()) {
// StringTokenizer st = new StringTokenizer(input.nextLine(), ",");
String[] tokens = input.nextLine().split(",");
if (tokens.length == 7) {
h = new Human();
h.setLastName(tokens[0]);
h.setFirstName(tokens[1]);
h.setAddress(tokens[2]);
h.setCiD(Integer.parseInt(tokens[3]));
h.setVisits(Integer.parseInt(tokens[4]));
h.setBalance(Double.parseDouble(tokens[5]));
} else {
p = new Pet(tokens[0], tokens[1], Integer.parseInt(tokens[2]), tokens[3], tokens[4]);
}
}
And for keeping track of which pet belongs to which human, you can append an arrayList of type Pet in Human class like below:
ArrayList<Pet> pets = new ArrayList<>();
And say you have another ArrayList of type Human named humans in the main function. So, you could append in if block like:
humans.add(h);
and in the else section, you could append in else block:
humans.get(humans.size()-1).pets.add(p);

You can try something like this -
Populate a map and then using that you can assign values according to your requirement.
public void differentiate(){
try {
Scanner scan=new Scanner(new BufferedReader(new FileReader("//your filepath")));
Map<String,List<String>> map=new HashMap<String, List<String>>();
while(scan.hasNextLine()){
List<String> petList=new ArrayList<String>();
String s=scan.nextLine();
String str[]=s.split(",");
String name=str[1]+" "+str[0];
int petCount=Integer.parseInt(str[str.length-1]);
for(int i=1;i<=petCount;i++){
String petString=scan.nextLine();
petList.add(petString);
}
map.put(name, petList);
}
Set<String> set=map.keySet();
for(String str:set){
System.out.println(str+" has "+map.get(str)+" pets");
}
}
catch (FileNotFoundException e) {
System.out.println(e.getMessage());
}
}