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Java Articles
Page 368 of 450
How to read data from .csv file in Java?
A library named OpenCSV provides API’s to read and write data from/into a.CSV file. Here it is explained how to read the contents of a .csv file using a Java program.Maven dependency com.opencsv opencsv 4.4 org.apache.commons commons-lang3 3.9 The CSVReader class of the com.opencsv package represents a simple CSV reader. While instantiating this class you need to pass a Reader object representing the file to be read as a parameter to its constructor. It provides methods named readAll() and readNext() to read the contents of a .csv fileUsing the readNext() methodThe readNext() ...
Read MoreHow to read certain number of elements from a file in Java?
To read a fixed number of elements from a file you can either read a required number of data elements from the file and process them or, read the entire file into a collection or an array and process it for every n element.ExampleFollowing Java program, reads the contents of a file 10 words at a time and prints them in a separate line.import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner; public class ReadingData { public static void main(String args[]) throws FileNotFoundException { //Creating an object of the File to read data File file = ...
Read MoreHow to read data from one file and print to another file in Java?
Java provides I/O Streams to read and write data where a Stream represents an input source or an output destination which could be a file, i/o devise, other programs, etc.In general, a Stream will be an input stream or, an output stream.InputStream − This is used to read data from a source.OutputStream − This is used to write data to a destination.Based on the data they handle there are two types of streams −Byte Streams − These handle data in bytes (8 bits) i.e., the byte stream classes read/write data of 8 bits. Using these you can store characters, videos, ...
Read MoreCan we use readUTF() to read a string from a .txt file in Java?
The readUTF() method of the java.io.DataOutputStream reads data that is in modified UTF-8 encoding, into a String and returns it.ExampleThe following Java program reads a UTF-8 text from a .txt file using the readUTF() method.import java.io.DataInputStream; import java.io.EOFException; import java.io.FileInputStream; import java.io.IOException; public class UTF8Example { public static void main(String args[]) { StringBuffer buffer = new StringBuffer(); try { //Instantiating the FileInputStream class FileInputStream fileIn = new FileInputStream("D:\test.txt"); //Instantiating the DataInputStream class DataInputStream inputStream = new DataInputStream(fileIn); ...
Read MoreReading UTF8 data from a file using Java
In general, data is stored in a computer in the form of bits (1 or, 0). There are various coding schemes available specifying the set of bytes represented by each character.Unicode (UTF) − Stands for Unicode Translation Format. It is developed by The Unicode Consortium. if you want to create documents that use characters from multiple character sets, you will be able to do so using the single Unicode character encodings. It provides 3 types of encodings.UTF-8 − It comes in 8-bit units (bytes), a character in UTF8 can be from 1 to 4 bytes long, making UTF8 variable width.UTF-16 ...
Read MoreHow to check if an URL is valid or not using Java?
The URL class of the java.net package represents a Uniform Resource Locator which is used to point a resource(file or, directory or a reference) in the worldwide web.This class provides various constructors one of them accepts a String parameter and constructs an object of the URL class. While passing URL to this method if you used an unknown protocol or haven’t specified any protocol this method throws a MalformedURLException.Similarly, the toURI() method of this class returns an URI object of the current URL. If the current URL is not properly formatted or, syntactically incorrect according to RFC 2396 this method throws ...
Read MoreRestrictions while declaring a generic (type) in Java
Generics is a concept in Java where you can enable a class, interface and, method, accept all (reference) types as parameters. In other words it is the concept which enables the users to choose the reference type that a method, constructor of a class accepts, dynamically. By defining a class as generic you are making it type-safe i.e. it can act up on any datatype.Restrictions on genericsYou cannot use generics in certain ways and in certain scenarios as listed below −You cannot use primitive datatypes with generics.class Student{ T age; Student(T age){ this.age = age; ...
Read MoreHow to find If a given String contains only letters in Java?
To verify whether a given String contains only characters −Read the String.Convert all the characters in the given String to lower case using the toLower() method.Convert it into a character array using the toCharArray() method of the String class.Find whether every character in the array is in between a and z, if not, return false.ExampleFollowing Java program accepts a String from the user and displays whether it is valid or not.import java.util.Scanner; public class StringValidation{ public boolean validtaeString(String str) { str = str.toLowerCase(); char[] charArray = str.toCharArray(); for (int i ...
Read MoreComparing Strings with (possible) null values in java?
Strings in Java represents an array of characters. They are represented by the String class.Using compareTo() methodThe compareTo() method of the String class two Strings (char by char) it also accepts null values. This method returns an integer representing the result, if the value of the obtained integer is −0: Given two Strings are equal or, null.1 or less: The current String preceeds the argument.1 or more: The current String succeeds the argument.Exampleimport java.util.Scanner; public class CompringStrings { public static void main(String args[]) { Scanner sc = new Scanner(System.in); System.out.println("Enter your first string ...
Read MoreHow to convert Date to String in Java 8?
The java.time package of Java provides API’s for dates, times, instances and durations. It provides various classes like Clock, LocalDate, LocalDateTime, LocalTime, MonthDay, Year, YearMonth etc. Using classes of this package you can get details related to date and time in much simpler way compared to previous alternatives.Java.time.LocalDate − This class represents a date object without time zone in ISO-8601 calendar system. The now() method of this class obtains the current date from the system clock.The toString() method of the LocalDate class converts the date value of the current Date object in to String and returns it.ExampleFollowing Java example accepts ...
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