Java Read From File and Parse Files.lines
How to load information from CSV file in Java - Example
You tin can load information from a CSV file in a Java programme by using BufferedReader class from thejava.io package. You tin read the file line by line and convert each line into an object representing that information. Really, in that location are a couple of ways to read or parse CSV files in Java e.thou. you lot can utilize a third-political party library similar Apache commons CSV or you can use Scanner class, but in this example, nosotros volition use the traditional style of loading CSV files using BufferedReader.
Here are the steps to load data from CSV file in Java without using any third-party library :
- Open CSV file using FileReader object
- Create BufferedReader from FileReader
- Read file line past line using readLine() method
- Split each line on comma to go an array of attributes using String.split() method
- Create an object of Volume class from String array using new Book()
- Add those object into ArrayList using add() method
- Return the List of books to the caller
And hither is our sample CSV file which contains details of my favorite books. It's called books.csv , each row represents a book with the title, price, and author information. The showtime cavalcade is the championship of the book, the 2nd cavalcade is the price, and the tertiary column is the author of the book.
Constructive Coffee,42,Joshua Bloch
Head Kickoff Java,39,Kathy Sierra
Caput First Design Pattern,44,Kathy Sierra
Introduction to Algorithm,72,Thomas Cormen
Pace by Step guide to load a CSV file in Java
Permit's go through each step to observe out what they are doing and how they are doing :
1. Reading the File
To read the CSV file we are going to use a BufferedReader in combination with a FileReader. FileReader is used to read a text file in the platform'south default graphic symbol encoding, if your file is encoded in other character encodings then you should use InputStreamReader instead of FileReader class. Nosotros will read one line at a time from the file using readLine() method until the EOF (end of file) is reached, in that case,readLine() will return a zippo.
ii. Carve up comma separated String
We take the string that we read from the CSV file and split it upward using the comma as the 'delimiter' (considering it's a CSV file). This creates an array with all the columns of the CSV file as we desire, even so, values are still in Strings, so we need to catechumen them into proper blazon e.1000. prices into float type as discussed in my post how to convert String to bladder in Coffee.
Once we got all the attribute values, we create an object of the Volume class past invoking the constructor of the volume as anew Book() and laissez passer all those attributes. One time we Book objects then we simply add them to our ArrayList.
Java Program to load data from CSV file
Here is our total program to read a CSV file in Coffee using BufferedReader. It's a good case of how to read data from a file line past line, split cord using a delimiter, and how to create objects from a String assortment in Java. Once you load information into the program you tin can insert it into a database, or you can persist into some other format or you tin can send it over the network to another JVM.
import java.io.BufferedReader; import coffee.io.IOException; import coffee.nio.charset.StandardCharsets; import java.nio.file.Files; import coffee.nio.file.Path; import java.nio.file.Paths; import java.util.ArrayList; import java.util.List; /** * Simple Java program to read CSV file in Java. In this program nosotros will read * list of books stored in CSV file as comma separated values. * * @author WINDOWS eight * */ public class CSVReaderInJava { public static void main(String... args) { List<Volume> books = readBooksFromCSV("books.txt"); // let's print all the person read from CSV file for (Book b : books) { System .out.println(b); } } private static List<Book> readBooksFromCSV(String fileName) { List<Book> books = new ArrayList<>(); Path pathToFile = Paths .get(fileName); // create an case of BufferedReader // using try with resource, Java vii feature to close resources endeavour (BufferedReader br = Files .newBufferedReader(pathToFile, StandardCharsets .US_ASCII)) { // read the first line from the text file Cord line = br.readLine(); // loop until all lines are read while (line != null) { // utilise string.split to load a cord array with the values from // each line of // the file, using a comma as the delimiter String[] attributes = line.split(","); Book volume = createBook(attributes); // calculation book into ArrayList books.add(book); // read next line before looping // if end of file reached, line would be null line = br.readLine(); } } grab (IOException ioe) { ioe.printStackTrace(); } return books; } private static Book createBook(Cord[] metadata) { String proper name = metadata[0]; int price = Integer .parseInt(metadata[1]); String author = metadata[2]; // create and render volume of this metadata render new Book(name, cost, author); } } form Book { individual Cord proper noun; individual int toll; private Cord author; public Book(String name, int price, String author) { this.proper noun = proper name; this.cost = price; this.author = author; } public Cord getName() { return proper noun; } public void setName(Cord name) { this.name = name; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } public Cord getAuthor() { return author; } public void setAuthor(String author) { this.author = author; } @Override public String toString() { return "Book [name=" + proper name + ", price=" + price + ", author=" + author + "]"; } } Output Book [proper name= Constructive Java, toll= 42, author= Joshua Bloch] Volume [proper name= Head First Java, price= 39, author= Kathy Sierra] Book [name= Head Outset Design Pattern, price= 44, writer= Kathy Sierra] Book [name= Introduction to Algorithm, price= 72, author= Thomas Cormen]
That's all about how to load CSV files in Java without using any third-political party library. You have learned how to employ BufferedReader to read information from CSV files and then how to split up comma-separated String into String array by using the String.split() method.
If y'all similar this tutorial and interested to learn more almost how to deal with files and directories in Java, y'all can check out the post-obit Java IO tutorial :
- How to read Excel Files in Coffee using Apache POI? [case]
- How to suspend data into an existing file in Java? [example]
- 2 means to read a file in Java? [tutorial]
- How to create a file or directory in Coffee? [example]
- How to read a text file using the Scanner class in Coffee? [answer]
- How to write content into a file using BufferedWriter form in Java? [case]
- How to read username and password from the command line in Java? [example]
- How to read Date and Cord from Excel file in Coffee? [tutorial]
Though you read CSV files in Java even more than easily by using a tertiary-party library like Apache commons CSV, knowing how to exercise it using pure Java will aid you lot to acquire central classes from JDK.
Source: https://www.java67.com/2015/08/how-to-load-data-from-csv-file-in-java.html
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