Basics – Scanner, System.in, System.out.println()

SCANNER CLASS:

Scanner class is used to get input from user.

• Scanner is a predefined class in java
• Scanner is a final class. We can’t inherited Scanner class.

Import the scanner class:

• Scanner class presented in java.util package.
• We want to import the package, before using the scanner class.

import java.util.Scanner;

Create Scanner Object:

Scanner sc = new Scanner(System.in);

• Here, Scanner is class.
• sc is an object of Scanner class

System.in:

Scanner(System.in);

• Above line is the Scanner Constructor.
• Passing System.in as a parameter.

SYSTEM CLASS:

• System is a predefined class in java.
• System class Presented in java.lang package
  • java.lang package is a default package in Java.
  • Therefore, there is no need to import it explicitly.
• System class is a final class. So, we can’t inherited this class.
• System class can’t be instantiated. i.e. Can’t create objects for system class.
• Because System class have private constructor.
• System class properties are static in nature. so we can call those properties by class name.
• The System class supports following class.
  • Java Predefined Class for Standard Input – InputStream Class
  • Java Predefined Class for Standard Output – PrintStream Class

InputStream Class:

• InputStream is a predefined class in java
• It is presented in java.io package
• This is abstract class.
  • We can’t create object for abstract class.
  • We can create object reference for abstract class

PrintStream Class:

• PrintputStream is a predefined class in java.
• It is presented in java.io package

System.in: [Standard input]

• System –> Predefined class
• in
  • in -> static member of system class
  • in -> object of InputStream class

System.out.println( ): [Standard output]

• System –> Predefined class in java.lang package
• out
  • out -> Static member of the System class.
  • out -> Object of PrintStream Class
• println() -> PrintStream method

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Scanner Methods:

• Scanner class have many methods to read the input of different datatype from user.
• We can access those methods by Scanner class object.

https://www.programiz.com/java-programming/scanner

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Ex 1:

import java.util.Scanner;

public class Demo1 
{
	public static void main(String[] args) 
	{

		// creates an object of Scanner
		// System.in --> takes input from the keyboard

		Scanner sc = new Scanner(System.in);

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

		// Scanner method calling based on input data type
		
		String name = sc.nextLine();

		// prints the input
		
		System.out.println("Welcome Ms." + name);
	}
}

Output:

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Ex 2:

import java.util.Scanner;

public class Demo1 {
	public static void main(String[] args) 
	{

		// creates a Scanner object
		// System.in --> takes input from the keyboard
		
		Scanner sc = new Scanner(System.in);

		System.out.println("Enter an integer: ");

		// Scanner method calling based on input data type
		
		int data1 = sc.nextInt();

		System.out.println("Using nextInt(): " + data1);
	}
}

Output:

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Ex 3:

import java.util.Scanner;

class Demo1 {
  public static void main(String[] args) {

    // creates an object of Scanner
    Scanner sc = new Scanner(System.in);
    System.out.print("Enter your name: ");

    //reads the word
    String value1 = sc.next();

    System.out.println("Using next(): " + value1);

  }
}

Output:

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NOTE:

• nextLine( ) —> Print the line
• next( ) —> Print the first word. Divide the line by white space

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