Swap two numbers without using temporary variable in java

Swap two numbers without using temporary variable


public class swap1 {

    public static void main(String[] args) {

        float first = 18.0f, second = 64.5f;

        System.out.println("--Before swap--");
        System.out.println("First number = " + first);
        System.out.println("Second number = " + second);

        first = first - second;
        second = first + second;
        first = second - first;

        System.out.println("--After swap--");
        System.out.println("First number = " + first);
        System.out.println("Second number = " + second);
    }
}


When you run the program, the output will be:


--Before swap--
First number = 18.0
Second number = 64.5
--After swap--
First number = 64.5
Second number = 18.0
BUILD SUCCESSFUL (total time: 3 seconds)

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Write a Program to find factorial of a number entered by user

import java.util.Scanner;
public class Example1 {

    public static void main(String[] args) {

    //We will find the factorial of this number
        int number;
        System.out.println("Enter the number: ");
        Scanner scanner = new Scanner(System.in);
        number = scanner.nextInt();
        scanner.close();
        long fact = 1;
        int i = 1;
        while(i<=number)
        {
            fact = fact * i;
            i++;
        }
        System.out.println("Factorial of "+number+" is: "+fact);
    }
}

Output:-

Enter the number:

5

Factorial of 5 is: 120

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Example2 :-

Above program does not give correct result for calculating factorial of say 16.

 Because 16! is a large number and can't be stored in integer data type which is of 4 bytes.

To calculate factorial of say hundred we use BigInteger  class of java.math package.

import java.util.Scanner;
import java.math.BigInteger;

class Fact1
{
  public static void main(String args[])
  {
    int n, c;
    BigInteger inc = new BigInteger("1");
    BigInteger fact = new BigInteger("1");

    Scanner input = new Scanner(System.in);

    System.out.println("Input an integer");
    n = input.nextInt();

    for (c = 1; c <= n; c++) {
      fact = fact.multiply(inc);
      inc = inc.add(BigInteger.ONE);
    }

    System.out.println(n + "! = " + fact);
  }
}


Output:-

Input an integer
16
16! = 20922789888000

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import statement in java

Import statement in java

1. The import statement provides a convenient way to identify classes that you want to reference to your class.import java.util.Date;

2.You can import a single class or an entire package;

3. You can include multiple import statements.

import java.util.Date;

import java.util.Calender;

you could refer to a class using it's fully qualified namespace in your application, as in the following example.

java.util.Date date = new java.util.Date();

but that would lead to a lot of typing instead java provides the import statement to allow you to declare that you want a reference  a class  in another package.

Here's an example program that uses Scanner, with an import statement:

import java.util.Scanner;

public class ScannerTest{

  public static void main(String arg[]){

    // scanner gets its input from the console.

    Scanner scanner = new Scanner(System.in);

    String fname = "";

    // Get the user's name.

    System.out.print("Your name, adventurer? >");

    fname = scanner.next();

    System.out.println();

    // Print their name in a a message.

    System.out.println("Welcome, " + fname + " to  Java tutorial Blog!");

  }

}

We import just the class Scanner from java.util in the import statement in this program. If we'd been using multiple classes from java.util, we could have made all the classes in java.util accessible to us by using this import statement:

import java.util.*;

The * is a "regular expression operator" that will match any mixture of characters. Therefore, this import statement will import everything in java.util. If you have tried entering and running the example program above, you can alter the import statement to this one.

If we need multiple classes from different packages, we use an import statement for each package from which we need to import classes (or interfaces, or any other part of that package we need.) It's not unusual to see a sequence of import statements near the start of a program file:

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