Java Articles

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Regular Expression "^" (caret) Metacharacter in Java

Maruthi Krishna
Maruthi Krishna
Updated on 18-Nov-2019 721 Views

The subexpression/metacharacter “^” matches the beginning of a line. If you use this in a regular expression, it matches the sentence succeeding it in the input string.Example 1import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegexExample {    public static void main( String args[] ) {       String regex = "^Hi how are you";       String input = "Hi how are you welcome to Tutorialspoint";       Pattern p = Pattern.compile(regex);       Matcher m = p.matcher(input);       int count = 0;       while(m.find()) {          count++;     ...

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Algorithm to generate positive rational numbers in Java

sudhir sharma
sudhir sharma
Updated on 16-Oct-2019 888 Views

Rational Numbers − A number that is expressed in the form of p/q. Given the condition that p and q both should be integers and q should not be equal to 0.Positive rational numbers are those numbers whose final values are positive. For this, either p and q both should be positive or p and q both should be negative.In this problem to generate positive random numbers up to a given number. We have to generate a finite number of positive rational numbers to n i.e. we will find rational numbers between 1 to n. For this algorithm, we will ...

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Difference between the list() and listFiles() methods in Java

Maruthi Krishna
Maruthi Krishna
Updated on 15-Oct-2019 1K+ Views

The class named File of the java.io package represents a file or directory (path names) in the system. To get the list of all the existing files in a directory this class provides the list() and ListFiles() methods.The main difference between them is thatThe list() method returns the names of all files in the given directory in the form of a String array.The ListFiles() method returns the objects (File) of the files in the given directory, in the form of an array of type File.i.e. If you just need the names of the files within a particular directory you can ...

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Byte Streams in Java

Maruthi Krishna
Maruthi Krishna
Updated on 15-Oct-2019 8K+ Views

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, audios, images etc.The InputStream and OutputStream classes (abstract) are the super classes of all the input/output stream classes: classes that are used to read/write a stream of bytes. Following are the byte array stream classes provided by Java −InputStreamOutputStreamFIleInputStreamFileOutputStreamByteArrayInputStreamByteArrayOutputStreamObjectInputStreamObjectOutputStreamPipedInputStreamPipedOutputStreamFilteredInputStreamFilteredOutputStreamBufferedInputStreamBufferedOutputStreamDataInputStreamDataOutputStreamExampleFollowing Java program reads data from a particular file using FileInputStream and writes it to another, using FileOutputStream.import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; public class IOStreamsExample {    public static void main(String args[]) throws IOException { ...

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Program to replace all the characters in of a file with '#' except a particular word in Java

Maruthi Krishna
Maruthi Krishna
Updated on 14-Oct-2019 653 Views

The split() method of the String class. splits the current string around matches of the given regular expression. The array returned by this method contains each substring of this string that is terminated by another substring that matches the given expression or is terminated by the end of the string.The replaceAll() method of the String class accepts two strings representing a regular expression and a replacement String and replaces the matched values with given String.To replace all the characters in of a file with '#' except a particular word (one way) −Read the contents of a file to a String.Create ...

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How do we mix two strings and generate another in java?

Maruthi Krishna
Maruthi Krishna
Updated on 10-Oct-2019 14K+ Views

Strings are used to store a sequence of characters in Java, they are treated as objects. The String class of the java.lang package represents a String.You can create a String either by using the new keyword (like any other object) or, by assigning value to the literal (like any other primitive datatype).String stringObject = new String("Hello how are you"); String stringLiteral = "Welcome to Tutorialspoint";Concatenating StringsYou can concatenate Strings in Java in the following ways −Using the "+" operator − Java Provides a concatenation operator using this, you can directly add two String literalsExampleimport java.util.Scanner; public class StringExample {   ...

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Convert Iterator to Iterable in Java

AmitDiwan
AmitDiwan
Updated on 25-Sep-2019 1K+ Views

Let’s say the following is our Iterator with Integer values −Iteratoriterator = Arrays.asList(20, 40, 60, 80, 100, 120, 150, 200).iterator();Now, convert the Iterator to Iterable −Iterableiterable = StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, 0),false).collect(Collectors.toList());ExampleFollowing is the program to convert Iterator to Iterable in Java −import java.util.*; import java.util.stream.Collectors; import java.util.stream.StreamSupport; public class Demo {    public static void main(String[] args) {       Iteratoriterator = Arrays.asList(20, 40, 60, 80, 100, 120, 150, 200).iterator();       Iterableiterable = StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, 0), false).collect(Collectors.toList());       System.out.println("Iterable = ");       iterable.forEach(System.out::println);    } }OutputIterable = 20 40 60 80 100 120 150 200

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Convert an Iterator to Stream in Java

AmitDiwan
AmitDiwan
Updated on 25-Sep-2019 469 Views

At first, set an Interator −Iteratoriterator = Arrays.asList(50, 100, 200, 400, 500, 1000).iterator();Now, we have used stream −Streamstream = convertIterator(iterator);Above, the method convertIterator() is used for conversion. Following is the method −public static Stream convertIterator(Iterator iterator) {    return StreamSupport.stream(((Iterable) () -> iterator).spliterator(), false); }ExampleFollowing is the program to convert an Iterator to Stream in Java −import java.util.stream.*; import java.util.*; public class Demo {    public static Stream    convertIterator(Iterator iterator) {       return StreamSupport.stream(((Iterable) () -> iterator).spliterator(), false);    }    public static void main(String[] args) {       Iteratoriterator = Arrays.asList(50, 100, 200, ...

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Convert a Set of String to a comma separated String in Java

AmitDiwan
AmitDiwan
Updated on 25-Sep-2019 1K+ Views

Let us first create a set with string values −Setset = new HashSet(Arrays.asList("One", "Two", "Three", "Four", "Five", "Six"));Now, convert it to a comma separated string using String.join() −String str = String.join(", ", set);ExampleFollowing is the program to convert set of string to a comma separated string in Java −import java.util.*; public class Demo {    public static void main(String args[]) {       Setset = new HashSet(Arrays.asList("One", "Two", "Three", "Four", "Five", "Six"));       System.out.println("Set = " + set);       String str = String.join(", ", set);       System.out.println("Comma separated String: "+ str);    } ...

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Convert a List of String to a comma separated String in Java

AmitDiwan
AmitDiwan
Updated on 25-Sep-2019 625 Views

At first, let’s say the following is our List of String −List myList = new ArrayList(Arrays.asList("One", "Two", "Three", "Four"));Now, convert this to a comma separated string using String.join()String str = String.join(", ", myList);ExampleFollowing is the program to convert List of String to a comma separated String in Java −import java.util.*; public class Demo {    public static void main(String args[]) {       List myList = new ArrayList(Arrays.asList("One", "Two", "Three", "Four"));       System.out.println("List = " + myList);       // comma separated       String str = String.join(", ", myList);       System.out.println("String (Comma ...

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