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Input and output (I/O) in Java

Input and output (I/O) in Java involve the process of receiving data into a program (input) and sending data out of a program (output). Here's an overview of input and output in Java:


Input in Java:


1. Reading from Console:

   - Java provides the `Scanner` class to read input from the console.


   import java.util.Scanner;


   public class ConsoleInput {

       public static void main(String[] args) {

           Scanner scanner = new Scanner(System.in);


           System.out.print("Enter your name: ");

           String name = scanner.nextLine();

           System.out.println("Hello, " + name + "!");


           scanner.close();

       }

   }



2. Reading from Files:

   - Java's `FileInputStream`, `BufferedReader`, or `Scanner` can be used to read data from files.


   import java.io.BufferedReader;

   import java.io.FileReader;

   import java.io.IOException;


   public class FileInput {

       public static void main(String[] args) {

           try (BufferedReader reader = new BufferedReader(new FileReader("example.txt"))) {

               String line;

               while ((line = reader.readLine()) != null) {

                   System.out.println(line);

               }

           } catch (IOException e) {

               e.printStackTrace();

           }

       }

   }



Output in Java:


1. Writing to Console:

   - The `System.out.println()` method is commonly used for console output.


   public class ConsoleOutput {

       public static void main(String[] args) {

           System.out.println("Hello, World!");

       }

   }



2. Writing to Files:

   - Java's `FileOutputStream`, `BufferedWriter`, or `PrintWriter` can be used to write data to files.


   import java.io.BufferedWriter;

   import java.io.FileWriter;

   import java.io.IOException;


   public class FileOutput {

       public static void main(String[] args) {

           try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"))) {

               writer.write("Writing to a file in Java.");

           } catch (IOException e) {

               e.printStackTrace();

           }

       }

   }



3. Standard Output and Error Streams:

   - The `System.out` and `System.err` streams are used for standard output and error.


   public class StandardOutputError {

       public static void main(String[] args) {

           System.out.println("This is standard output.");

           System.err.println("This is standard error.");

       }

   }



These examples cover basic input and output operations in Java. The `java.util.Scanner` class is versatile for handling various types of input, and the `java.io` package provides a range of classes for file-based input and output operations. Understanding these concepts is fundamental for building interactive and data-driven Java applications.

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