Develop Reference

Searching data from arraylist

I am a newbie of c++.
Now I am doing a project need to read a customer list from a csv file and then search if there is a username like "Ali" and printout all the data about Ali.
How can I search "Ali" and printout all the data about Ali like CustomerNo , Name , PhoneNo and Status?
And if there is multiple data with "Ali" , how can I printout all of them either?
Here is my code:
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.Iterator;
public class LoadCustomer {
public static void main(String[] args) throws IOException{
System.out.println ("Load customer from file");
ArrayList<Customer> customers = readCustomerFromFile();
System.out.println (customers);
System.out.println ();
private static ArrayList<Customer> readCustomerFromFile() throws IOException{
ArrayList<Customer> customers = new ArrayList<>();
List<String> lines = Files.readAllLines(Paths.get("customer.csv"));
for (int i = 1 ; i < lines.size() ; i++){
String[] items = lines.get(i).split(",");
int customerNo = Integer.parseInt(items[0]);
int phoneNo = Integer.parseInt(items[2]);
customers.add (new Customer(customerNo,items[1],phoneNo,items[3]));
}
return customers;
}
}
Here is my Customer class:(added getName getter)
public class Customer {
private int customerNo;
private String name;
private int phoneNo;
private String status;
public Customer () {}
public Customer (int customerNo, String name, int phoneNo, String status){
this.customerNo = customerNo;
this.name = name;
this.phoneNo = phoneNo;
this.status = status;
}
public String getName(){
return name;
}
public String toString(){
return customerNo + " " + name + " " + phoneNo + " " + status;
}
public String toCSVString(){
return customerNo + "," + name + "," + phoneNo + "," + status;
}
}
And here is my data:
CustomerNo Name PhoneNo Status
1 Ali 12345 Normal
2 Siti 23456 Normal
3 Rone 78910 Normal
4 Jean 56789 Normal
5 Roby 28573 Normal
6 Ali 78532 Normal
Thank you very much for your attention.
Edited :
Here is my code for this program:
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
public class FindCustomer {
public static void main(String[] args) throws IOException{
System.out.println ("Load customer from file");
java.util.Map<String, List<Customer>> customers =
Files.lines(Paths.get("customer.csv"))
.map(line -> line.split(","))
.map(field -> new Customer(
Integer.parseInt(field[0]), field[1],
Integer.parseInt(field[2]), field[3]))
.collect(Collectors
.groupingBy(Customer::getName));
System.out.println (customers);
}
}

Bit of a broad question.
If you expect to do this a lot, and on a boatload of data, do what everybody else does when they are faced with a lot of relational data that they need to run queries on. Use a database, like postgres or h2. To interact with those from java, use JDBI or JOOQ.
If this is just a small simple text file and/or you're trying to learn some java, well, you still have two options here: You can loop through the data, or, you can build a mapping.
The loop option is simple:
for (Customer c : customers) if (c.getName().equals("Ali")) {
// do what you want here. 'c' holds the customer object of Ali.
}
But this does, of course, require a full run through all the entries every time. Another option is to build a mapping:
var map = new HashMap<String, Customer>();
for (Customer c : customers) map.put(c.getName(), c);
// map now maps a customer name to the customer object.
Customer ali = map.get("Ali");
maps have the advantage that they are near instant lookup. Even if the map contains a million entries, map.get(x) is (near) instant. A decent solution if you have lots of data + the need to do lots of lookups. But, you have to build a complete map for everything you care to query on. So, if you want to do lookups on name, and then later something like 'get all customers with a 6 digit phone number whose status is Normal', then, get a database.

As was suggested a map would be useful. You can create one on the fly as you read in the file.
Splits the line
creates a customer.
and groups it by name in a map.
Now the map will hold for each name, all customers that have that name.
Map<String, List<Customer>> customers =
Files.lines(Paths.get("customer.csv"))
.map(line -> line.split("\\s*,\\s*"))
.map(field -> new Customer(
Integer.parseInt(field[0]), field[1],
Integer.parseInt(field[2]), field[3]))
.collect(Collectors
.groupingBy(Customer::getName));
To get the List of customers for the name Ali do the following.
List<Customer> ali = customers.get("Ali");
Now it's up to you to format or otherwise use the list as required. You will still need to handle exceptions via try/catch.

Java Hash map / Array List Count distinct values

I am pretty new into programming and I have an assignment to make, but I got stuck.
I have to implement a program which will read a CSV file (1 million+ lines) and count how many clients ordered "x" distinct products on a specific day.
The CSV looks like this:
Product Name | Product ID | Client ID | Date
Name 544 86 10/12/2017
Name 545 86 10/12/2017
Name 644 87 10/12/2017
Name 644 87 10/12/2017
Name 9857 801 10/12/2017
Name 3022 801 10/12/2017
Name 3021 801 10/12/2017
The result from my code is:
801: 2 - incorrect
86: 2 - correct
87: 2 - incorrect
Desired output is:
Client 1 (801): 3 distinct products
Client 2 (86): 2 distinct products
Client 3 (87): 1 distinct product
Additionally,
If I want to know how many clients ordered 2 distinct products I would like a result to look like this:
Total: 1 client ordered 2 distinct products
If I want to know the maximum number of distinct products ordered in a day, I would like the result to look like this:
The maximum number of distinct products ordered is: 3
I tried to use a Hash Map and Multimap by Google Guava (my best guess here), but I couldn't wrap my head around it.
My code looks like this:
package Test;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.HashMultimap;
public class Test {
public static void main(String[] args) {
//HashMultimap<String, String> myMultimap = HashMultimap.create();
Map<String, MutableInteger> map = new HashMap<String, MutableInteger>();
ArrayList<String> linesList = new ArrayList<>();
// Input of file which needs to be parsed
String csvFile = "file.csv";
BufferedReader csvReader;
// Data split by 'TAB' in CSV file
String csvSplitBy = "\t";
try {
// Read the CSV file into an ArrayList array for easy processing.
String line;
csvReader = new BufferedReader(new FileReader(csvFile));
while ((line = csvReader.readLine()) !=null) {
linesList.add(line);
}
csvReader.close();
} catch (IOException e) {
e.printStackTrace();
}
// Process each CSV file line which is now contained within
// the linesList list Array
for (int i = 0; i < linesList.size(); i++) {
String[] data = linesList.get(i).split(csvSplitBy);
String col2 = data[1];
String col3 = data[2];
String col4 = data[3];
// Determine if Column 4 has the desired date
// and count the values
if (col4.contains("10/12/2017")) {
String key = col3;
if (map.containsKey(key)) {
MutableInteger count = map.get(key);
count.set(count.get() + 1);
} else {
map.put(key, new MutableInteger(1));
}
}
}
for (final String k : map.keySet()) {
if (map.get(k).get() == 2) {
System.out.println(k + ": " + map.get(k).get());
}
}
}
}
Any advise or suggestion on how this can be implemented would be greatly appreciated.
Thank you in advance guys.

You could store a Setof productIds per clientId, and just take the size of that.
As a Set does not allow duplicate values, this will effectively give you the distinct number of productIds.
Also, I recommend that you give your variables meaningful name instead of col2, k, map... This will make your code more readable.
Map<String, Set<String>> distinctProductsPerClient = new HashMap<String, Set<String>>();
// Process each CSV file line which is now contained within
// the linesList list Array
// Start from 1 to skip the first line
for (int i = 1; i < linesList.size(); i++) {
String line = linesList.get(i);
String[] data = line.split(csvSplitBy);
String productId = data[1];
String clientId = data[2];
String date = data[3];
// Determine if Column 4 has the desired date
// and count the values
if (date.contains("10/12/2017")) {
if (!distinctProductsPerClient.containsKey(clientId)) {
distinctProductsPerClient.put(clientId, new HashSet<>());
}
distinctProductsPerClient.get(clientId).add(productId);
}
}
for (final String clientId : distinctProductsPerClient.keySet()) {
System.out.println(clientId + ": " + distinctProductsPerClient.get(clientId).size());
}
More advanced solution using Stream API (requires Java 9)
If you introduce the class OrderData(that represents a single line in the CSV) like this:
private static class OrderData {
private final String productName;
private final String productId;
private final String clientId;
private final String date;
public OrderData(String csvLine) {
String[] data = csvLine.split("\t");
this.productName = data[0];
this.productId = data[1];
this.clientId = data[2];
this.date = data[3];
}
public String getProductName() {
return productName;
}
public String getProductId() {
return productId;
}
public String getClientId() {
return clientId;
}
public String getDate() {
return date;
}
}
you can replace the for loop with this:
Map<String, Set<String>> distinctProductsPerClient2 = linesList.stream()
.skip(1)
.map(OrderData::new)
.collect(groupingBy(OrderData::getClientId, mapping(OrderData::getProductId, toSet())));
But I reckon this might be a little bit to complex if you're new into programming (although it might be a good exercise if you would try to understand what the above code does).

Need an help to sort, Handle a tab seperated text file

Hi i have a text file(tab seperated).
I would like to open it, read it and filter the required columns just like we do in excel. Could someone help with a sample code.
I am stuck up with the concept on how to proceed further for the below steps.
Price has to sorted with DESC order before processing.
Always, First two column has to be printed in the output.
Other than the first two columns only the required column has to be printed based on the input given.
Input will be something like (Mango/purchased/top50). so it should pick only top50 "yet to buy" under "Mango" along with its respective first two columns.
Sample input file.
itemNumber Price Mango Apple Bannana
112201 purchased need to plan purchased
112202 55 yet to buy yet to buy purchased
112202 67 need to plan purchased purchased
112203 456 need to plan need to plan need to plan
112203 33 need to plan yet to buy need to plan
112204 456 need to plan yet to buy need to plan
112204 yet to buy purchased need to plan
112205 77 yet to buy purchased need to plan
112205 99 yet to buy purchased yet to buy
112206 0 yet to buy purchased yet to buy
The code is incomplete.
Here i am trying to add the heading of the file to an arraylist and adding the content to an another arraylist. Then trying to compare them using index number. Is this way correct ?
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
public class main {
#SuppressWarnings({ "resource", "unused" })
public static void main(String[] args) throws IOException {
ZipFile zipFile = new ZipFile(
"filename.tsv.zip");
Enumeration<? extends ZipEntry> entries = zipFile.entries();
while (entries.hasMoreElements()) {
String fruit = "Mango";
String mappingstatus = "purchased";
// reading a file
ZipEntry entry = entries.nextElement();
InputStream stream = zipFile.getInputStream(entry);
InputStreamReader read = new InputStreamReader(stream);
BufferedReader br = new BufferedReader(read);
// creating a new list
List<String> heading = new ArrayList<String>();
String[] a = br.readLine().split("\t");
heading = Arrays.asList(a);
List<String> content = new ArrayList<String>();
String s;
while ((s = br.readLine()) != null) {
String[] b = br.readLine().split("\t");
content = Arrays.asList(b);
}
}
}
}

Try this
class Item implements Comparable<Item> {
int itemNumber;
int price;
String mango;
String apple;
String bannana;
public Item(int itemNumber, int price, String mango, String apple, String bannana) {
this.itemNumber = itemNumber;
this.price = price;
this.mango = mango;
this.apple = apple;
this.bannana = bannana;
}
//GETTERS
#Override
public int compareTo(Item compareItem) {
int comparePrice = ((Item) compareItem).getPrice();
//ascending order
//return this.price - comparePrice;
//descending order
return comparePrice - this.price;
}
}
public static void main(String[] args) {
List<Item> items = new ArrayList<>();
//populate the items list by creating an Item for every line you read.
//Handle null price values
Collections.sort(items);
//assuming input is some like 'Mango/purchased/top50'
String input = "Mango/purchased/top50";
String[] parts = input.split("/");
int max = Integer.parseInt(parts[2].substring(3));
List<Item> result = new ArrayList<>();
for (int i = 0; i < items.size() && result.size() < max; i++) {
Item item = items.get(i);
if ((parts[0].equals("Mango") && item.getMango().equals(parts[1]))
|| (parts[0].equals("Apple") && item.getApple().equals(parts[1]))
|| (parts[0].equals("Bannana") && item.getBannana().equals(parts[1]))) {
result.add(item);
}
}
}
Complete the commented sections and it must work. More references about sorting here: Sorting

How do you send an array to an arraylist?

I am have trouble creating an array or object(with multiple fields) and sending it to an array-list. Any help would be greatly appreciated. I have spent hours looking through every video on YouTube with the words object and array-list in them and have been unable to find much help.
The program needs to prompt the user to pick a option (1. AddItem) then prompt the user for the name and format (dvd, vhs) and save multiple objects with these variables in an array-list. I either keep having the location where it is saved in memory returned to me or instead of multiple objects one large object is created.
Library:
import java.util.Scanner;
import java.util.ArrayList;
public class Library {
static ArrayList<Object> items = new ArrayList<Object>();
static int menuOption;
static Scanner scan = new Scanner(System.in);
public static void main(String args[]) {
String title, format;
boolean right = false;
do{
displayMenu();
if (menuOption == 1){
System.out.println("Enter Title: ");
title = scan.next();
System.out.println("Enter format: ");
format = scan.next();
addNewItem(title, format);
} else {System.out.println(items);
}
} while (!right);
}
static int displayMenu(){
System.out.println("Menu: ");
System.out.println("1. Add New Item");
menuOption = scan.nextInt();
return menuOption;
}
static void addNewItem(String title, String format){
MediaItem b = new MediaItem();
b.setTitle(title);
b.setFormat(format);
items.add(b);
}
}
MediaItem:
public class MediaItem {
String title;
String format;
MediaItem(){
title = null;
format = null
}
MediaItem(String title, String format){
title = new String();
format = new String();
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getFormat() {
return format;
}
public void setFormat(String format) {
this.format = format;
}
}

The program will run if you:
1 - Change the line
static ArrayList<Object> items = new ArrayList<Object>();
to
static ArrayList<MediaItem> items = new ArrayList<MediaItem>();
2 - Change the line
System.out.println( items );
to
for ( MediaItem mi : items )
{
System.out.println( mi.getTitle() + ", " + mi.getFormat() );
}
3 - Insert a ";" at the end of the line
format = null
I did it here and it worked.

I either keep having the location where it is saved in memory returned to me
I am guessing you ran into this when you tried to either use System.out.println() to print a MediaItem, or you otherwise tried to automatically convert an object to a string. Whatever approach you took when you were seeing the memory addresses is probably the right way to do it, your problem was only in your displaying of the data.
Consider:
MediaItem item = ...;
System.out.println(item);
By default, Java doesn't know how to convert arbitrary objects to strings when you do stuff like that, and so it just spits out the class name and memory address. You either need to print the fields separately (e.g. Java knows how to display a String already), like:
System.out.println("Title: " + item.getTitle() + " Format: " + item.getFormat());
Or you can override toString() (declared in Object) to provide a custom string conversion:
class MediaItem {
...
#Override public String toString () {
return "Title: " + title + " Format: " + format;
}
}
And then you can print it directly:
System.out.println(item);
It is the default base implementation of Object.toString() that produces those strings with the memory address in them.
Based on your description, I'm guessing you had a roughly working implementation but ran into this issue and ended up changing around (and breaking) a bunch of other unrelated things to try and fix it.

read a txt file and manipulate the readLine strings

I would like to take this format:
//Game, Team, Player, Position, Order, Sub----Not part of file
331027,24,7912,CF,1,1
331028,22,7913,P,1,1
331028,22,5909,1B,2,1
331028,22,8394,P,2,2
And display this data(order) based on a higher number for sub in a given order and the output will become:
331027,24,7912,CF,1 //player 7912 goes first for team 24
331028,22,7913,P,1 //player 7913 goes first for team 22
331028,22,8394,P,2 // player 8394 goes second for team 22 because he/she has higher 'Sub' order
UPDATE:
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class BattingOrder {
String game_ID;
String team_ID;
String player_ID;
String position;
String battingOrder;
String subOrder;
public BattingOrder(String game, String team, String player, String place,
String batter, String sub) {
game_ID = game;
team_ID = team;
player_ID = player;
position = place;
battingOrder = batter;
subOrder = sub;
}
#Override
public String toString() {
return game_ID + "," + team_ID + "," + player_ID + "," + position + ","
+ battingOrder;
}
public static void main(String[] args) throws IOException {
FileInputStream fstream = new FileInputStream(
"BatterInfo.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
List<BattingOrder> sortList = new ArrayList<BattingOrder>();
for (String line; (line = br.readLine()) != null;) {
String delims = "[,]";
String[] parsedData = line.split(delims);
sortList.add(new BattingOrder(parsedData[0], parsedData[1],
parsedData[2], parsedData[3], parsedData[4], parsedData[5]));
}
for (BattingOrder order : sortList) {
System.out.println(order);
}
br.close();
}
}
Current Output:
331027,24,7912,CF,1
331028,22,7913,P,1
331028,22,5909,1B,2 //This should be replaced by bottom 'string' because the subOrder is higher.
331028,22,8394,P,2
I want:
331027,24,7912,CF,1
331028,22,7913,P,1
331028,22,8394,P,2
How might the logic look in pseudo-code?

From http://www.mkyong.com/java/how-to-sort-an-arraylist-in-java/ and http://www.mkyong.com/java/java-object-sorting-example-comparable-and-comparator/ and the above answer from Java Devil
I think the best method would be to put each BattingOrder object into a collection i.e. ArrayList and use Collections.sort
List<BattingOrder> unsortList = new ArrayList<BattingOrder>();
Add a constructor to BattingOrder or just manually set the values inside your for loop in main to either split the input string from the file or accept the preparsed values
then after the for loop is complete call Collections.sort and pass in a custom Comparator, you have most of the required code commented out should be no issue.
for (String line; (line = br.readLine()) != null;) {
// String delims = "[,]";
// String[] parsedData = line.split(delims);
//Split and assign the values to a new BattingOrder object here either in a
//constructor for BattingObject or here and pass in the values from the file
unsortList.add(new BattingOrder(line));
}
After the loop is complete call our custom sort function
Collections.sort(unsortList ,new Comparator<BattingOrder>(){
#Override
public int compare(BattingOrder one, BattingOrder two) {
Integer orderOne = Integer.parseInt(one.battingOrder);
Integer orderTwo = Integer.parseInt(two.battingOrder);
//ascending order
return orderOne.compareTo(orderTwo);
//descending order
//return orderTwo.compareTo(orderOne);
}
});
and bam should be sorted
I can't test this code atm at work no Java compiler but it should be close if not correct
Good luck ;)
Edit 3 (Clarification)
I was hoping you might add some more detail overnight, (Original input with index)
Index Pos Order Sub
1 CF 1 1
2 P 1 1
3 1B 2 1
4 P 2 2
Atm you don't have sufficient sort logic, disappearing index 3 is possible with the lower subOrder but 1 & 2 are interchangeable as they both have subOrder of 1 and order of 1 so whichever was read in first will be at the top of the list i think.
This code should sort them in some random order (Determined by the order they are read in by basically)
then will delete any that have a matching battingOrder and a lower subOrder
I hope thats close to what you want anyway the sort is pretty good just not great logic the delete isn't very efficient but its all I have to go on atm
All the casts could be removed by storing the integers as ints rather than strings
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class BattingOrder
{
String game_ID;
String team_ID;
String player_ID;
String position;
String battingOrder;
String subOrder;
public BattingOrder(String game, String team, String player, String place, String batter, String sub) {
game_ID = game;
team_ID = team;
player_ID = player;
position = place;
battingOrder = batter;
subOrder = sub;
}
#Override
public String toString()
{
return game_ID + "," + team_ID + "," + player_ID + "," + position + "," + battingOrder;
}
public static void main(String[] args) throws IOException
{
FileInputStream fstream = new FileInputStream("BatterInfo.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String delims = "[,]";
List<BattingOrder> battingOrders = new ArrayList<BattingOrder>();
for (String line; (line = br.readLine()) != null;)
{
String[] parsedData = line.split(delims);
battingOrders.add(new BattingOrder(parsedData[0], parsedData[1], parsedData[2], parsedData[3], parsedData[4], parsedData[5]));
}
br.close();
System.out.println("Unordered");
for (BattingOrder order : battingOrders)
{
System.out.println(order);
}
Collections.sort(battingOrders ,new Comparator<BattingOrder>(){
#Override
public int compare(BattingOrder one, BattingOrder two)
{
if(one.battingOrder.equals(two.battingOrder))
{
Integer subOrderOne = Integer.parseInt(one.subOrder);
Integer subOrderTwo = Integer.parseInt(two.subOrder);
return subOrderOne.compareTo(subOrderTwo);
}
Integer orderOne = Integer.parseInt(one.battingOrder);
Integer orderTwo = Integer.parseInt(two.battingOrder);
return orderOne.compareTo(orderTwo);
}
});
System.out.println("Ordered");
for (BattingOrder order : battingOrders)
{
System.out.println(order);
}
List<BattingOrder> toDelete = new ArrayList<BattingOrder>();
for (BattingOrder one : battingOrders)
{
for (BattingOrder two : battingOrders)
{
if(one.battingOrder.equals(two.battingOrder))
{
Integer subOrderOne = Integer.parseInt(one.subOrder);
Integer subOrderTwo = Integer.parseInt(two.subOrder);
if(subOrderOne < subOrderTwo)
{
toDelete.add(one);
}
else if(subOrderOne > subOrderTwo)
{
toDelete.add(two);
}
}
}
}
battingOrders.removeAll(toDelete);
System.out.println("Final");
for (BattingOrder order : battingOrders)
{
System.out.println(order);
}
}
}

You will need to read in all the lines from the text file first and then sort them.
As you read each line store it into a List of either Strings or better yet would be to create an object which represents each line - Which you pretty much have here already. So for each line you would want split by comma as you have comments and assign the values to a new instance of your object then add this to a list.
You can then sort the list using a comparator on these objects in the list using something like this
Collections.sort(yourList,new Comparator<BattingOrder>(){
#Override
public int compare(BattingOrder b1, BattingOrder b2)
{
//Your comparison code goes here
}
});