JAVA Basic Programs

JAVA Basic Programs

Creating Hello java example

class Simple{  

    public static void main(String args[]){  

     System.out.println("Hello Java");  

    }  

}  

Output:Hello Java

Understanding first java program

Let's see what is the meaning of class, public, static, void, main, String[], System.out.println().

Ø  class keyword is used to declare a class in java.

Ø  public keyword is an access modifier which represents visibility, it means it is visible to all.

Ø  static is a keyword, if we declare any method as static, it is known as static method. The core advantage of static method is that there is no need to create object to invoke the static method. The main method is executed by the JVM, so it doesn't require to create object to invoke the main method. So it saves memory.

Ø  void is the return type of the method, it means it doesn't return any value.

Ø  main represents startup of the program.

Ø  String[] args is used for command line argument. We will learn it later.

Ø  System.out.println() is used print statement.

 Even Odd Number Example

public class FindEvenOrOddNumber {

public static void main(String[] args) {
  //create an array of 10 numbers

   int[] numbers = new int[]{1,2,3,4,5,6,7,8,9,10};

  for(int i=0; i < numbers.length; i++){
  /*

   * use modulus operator to check if the number is even or odd. 

    * If we divide any number by 2 and reminder is 0 then the number is

    * even, otherwise it is odd.

    */

     if(numbers[i]%2 == 0)

    System.out.println(numbers[i] + " is even number.");

    else

   System.out.println(numbers[i] + " is odd number.");

                         }

                  }

} 

Output of the program would be

1 is odd number.

2 is even number.

3 is odd number.

4 is even number.

5 is odd number.

6 is even number.

7 is odd number.

8 is even number.

9 is odd number.

1    10 is even number.

Factorial Example

public class NumberFactorial {

 public static void main(String[] args) {

 int number = 5;

 / / Factorial of any number is !n For example, factorial of 4 is 4*3*2*1.

 int factorial = number;

 for(int i =(number - 1); i > 1; i--)

  {

      factorial = factorial * i;

  }

  System.out.println("Factorial of a number is " + factorial);

        }

}

Output of the Factorial program would be

Factorial of a number is 120

Swap Numbers Without Using Third Variable Java Example

public class SwapElementsWithoutThirdVariableExample {

 public static void main(String[] args) {

 int num1 = 10;

 int num2 = 20;

 System.out.println("Before Swapping");

 System.out.println("Value of num1 is :" + num1);

 System.out.println("Value of num2 is :" +num2);

 //add both the numbers and assign it to first

  num1 = num1 + num2;

  num2 = num1 - num2;

  num1 = num1 - num2;

  System.out.println("Before Swapping");

  System.out.println("Value of num1 is :" + num1);

  System.out.println("Value of num2 is :" +num2);

        }

 }

 Output

Before Swapping

Value of num1 is :10

Value of num2 is :20

Before Swapping

Value of num1 is :20

Value of num2 is :10

 Print Alphabet

class Alphabets

{

   public static void main(String args[])

   {

        char ch; 

        for( ch = 'a' ; ch <= 'z' ; ch++ )

         System.out.print(ch);

   }
}

 Output

abcdefghijklmnopqrstuvwxz

Program to display the prime numbers from 1 to 100

It will display the prime numbers between 1 and 100.

class PrimeNumbers

{

   public static void main (String[] args)

   {                   

       int i =0;

       int num =0;

       //Empty String

       String  primeNumbers = "";

       for (i = 1; i <= 100; i++)        

       {                              

          int counter=0;      

          for(num =i; num>=1; num--)

              {

             if(i%num==0)

                 {

                        counter = counter + 1;

                 }

              }

              if (counter ==2)

              {

                 //Appended the Prime number to the String

                 primeNumbers = primeNumbers + i + " ";

              }        

       }   

       System.out.println("Prime numbers from 1 to 100 are :");

       System.out.println(primeNumbers);

   }

}

Output:

Prime numbers from 1 to 100 are :

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

Fahrenheit to Celsius

import java.util.*;

 class FahrenheitToCelsius {

 public static void main(String[] args) {

 float temperatue = 100;

 System.out.println(" temperatue in Fahrenheitis 100");

 temperatue = ((temperatue - 32)*5)/9;

 System.out.println("Temperatue in Celsius = " + temperatue);

  }

}

Output:

 temperatue in Fahrenheit is 100

Temperatue in Celsius =37.77778

prints multiplication table of a number

import java.util.Scanner;

class MultiplicationTable

{

   public static void main(String args[])

   {

      int n=4, c;

      System.out.println("Multiplication table of "+n+" is :-");

      for ( c = 1 ; c <= 10 ; c++ )

         System.out.println(n+"*"+c+" = "+(n*c));

   }

}

Output

Enter an integer to print it's multiplication table 4

Multiplication table of 4  is :-

4*1=4

4*2=8

4*3=12

4*4=16

4*5=20

4*6=24

4*7=28

4*8=32

4*9=36

4*10=40

Finds largest of three numbers 

import java.util.Scanner;

 class LargestOfThreeNumbers

{

   public static void main(String args[])

   {

      int x=5, y=54, z=34;

       if ( x > y && x > z )

         System.out.println("First number is largest.");

      else if ( y > x && y > z )

         System.out.println("Second number is largest.");

      else if ( z > x && z > y )

         System.out.println("Third number is largest.");

      else  

         System.out.println("Entered numbers are not distinct.");

   }

}

Output:

Second number is largest