Java programs

 List of Java Programs
1) WAP to display the List of even numbers
2)Factorial of a number
3) Compare Two Numbers using else-if
4) Determine If Year Is Leap Year
5)Fibonacci Series
6)Palindrome Number
7)Generate prime numbers between 1 & given number100
8)Pyramid of stars using nested for loops
9)Reversed pyramid using for loops & decrement operator.
10) Nested Switch
11)Calculate Circle Area using radius
12) Factorial of a number using recursion
13)Pyramid of numbers using for loops
14)To Find Maximum of Two Numbers.
15)To Find Minimum of Two Numbers using conditional operator
16)Write a program that will read a float type value from the keyboard and print the following output.
->Small Integer not less than the number. ->Given Number.
->Largest Integer not greater than the number. 
17)Write a program to generate 5 Random nos. between 1 to 100, and it should not follow with decimal point.
18) Write a program to display a greet message according to Marks obtained by student
19)Write a program to find SUM AND PRODUCT of a given Digit.
20)Write a program to find sum of all integers greater than 100 and less than 200 that are divisible by 7
21)Write a program to concatenate string using for Loop
22) Program to Display Multiplication Table
23)Write a program to Swap the values
24)Write a program to convert given no. of days into months and days.(Assume that each month is of 30 days)
25) Write a program to Display Invert Triangle using while loop.
26)Write a program to find whether given no. is Armstrong or not.
27)switch case demo
28) Write a program to generate Harmonic Series.
29)  Write a program to find average of consecutive N Odd numbers and even numbers.
30) Display Triangle as follow: (using for loops)
1
2 3
4 5 6
78910...N*/



Programs to work out

1)WAP to display a color name depending on color value using switch.
2)Accepting single character, int, float, string and double value from the keyboard.
3)To grade the students using switch and if-else.
4)To compute the power of 2 using for loop
5)To find the sum of the digits of a given integer number.
6)Given the month , identify the season using switch.

==================================================
1)WAP to display the List of even numbers
/*
List Even Numbers Java Example
This List Even Numbers Java Example shows how to find and list even numbers between 1 and any given number.
*/
public class ListEvenNumbers {
    public static void main(String[] args) {
        //define limit
        int limit = 50;
        System.out.println("Printing Even numbers between 1 and " +
            limit);
        for (int i = 1; i <= limit; i++) {

            // if the number is divisible by 2 then it is even if( i % 2 == 0){
            System.out.print(i + " ");
        }
    }
}

}

========================
2)Factorial of a number
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);
    }

}
================================
3)Compare Two Numbers using else-if
/*
Compare Two Numbers Java Example
This Compare Two Numbers Java Example shows how to compare two numbers using if else if statements.
*/
public class CompareTwoNumbers {
    public static void main(String[] args) {
        //declare two numbers to compare
        int num1 = 324;
        int num2 = 234;
        if (num1 > num2) {
            System.out.println(num1 + " is greater than " + num2);
        } else if (num1 < num2) {
            System.out.println(num1 + " is less than " + num2);
        } else {
            System.out.println(num1 + " is equal to " + num2);
        }
    }
}
=======================
#4Determine If Year Is Leap Year
/*
Determine If Year Is Leap Year Java Example
This Determine If Year Is Leap Year Java Example shows how to determine whether the given year is leap year or not.
*/
public class DetermineLeapYearExample {
    public static void main(String[] args) {
        //year we want to check
        int year = 2004;
        //if year is divisible by 4, it is a leap year
        if (year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))
        System.out.println("Year " + year + " is a leap year");
        else
            System.out.println("Year " + year + " is not a leap year");
    }

}

=========================
 5)Fibonacci Series
/* Fibonacci Series Java Example
This Fibonacci Series Java Example shows how to create and print Fibonacci Series using Java.
*/
public class JavaFibonacciSeriesExample {
    public static void main(String[] args) {
        //number of elements to generate in a series int limit = 20;
        long[] series = new long[limit];
        //create first 2 series elements
    }
}
series[0] = 0;
series[1] = 1;
//create the Fibonacci series and store it in an array 
for(int i=2; i < limit; i++){
series[i] = series[i - 1] + series[i - 2];
}
//print the Fibonacci series numbers
System.out.println("Fibonacci Series upto " + limit);
for (int i = 0; i < limit; i++) {
    System.out.print(series[i] + " ");
}
/*
Output of the Fibonacci Series Java Example would be Fibonacci Series upto 20

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 */

==============
6)Palindrome Number
/*
This program shows how to check
for in the given list of numbers whether each number is palindrome or not
*/
public class JavaPalindromeNumberExample {
    public static void main(String[] args) {
        //array of numbers to be checked
        int numbers[] = new int[] {121,13,34,11,22,54};
        //iterate through the numbers
        for (int i = 0; i < numbers.length; i++) {
            int number = numbers[i];
            int reversedNumber = 0;
            int temp = 0;
            /*
            * If the number is equal to it's reversed number, then * the given             *  number is a palindrome number.
            * For ex,121 is a palindrome number while 12 is not.
            */
            //reverse the number
            while (number > 0) {
                temp = number % 10;
                number = number / 10;
                reversedNumber = reversedNumber * 10 + temp;
            }
        }
    }

if (numbers[i] == reversedNumber)
    System.out.println(numbers[i] + " is a palindrome");
else
    System.out.println(numbers[i] + " not a palindrome ");
}
/*
Output of Java Palindrome Number Example would be 121 is a palindrome number
13 is not a palindrome number
34 is not a palindrome number
11 is a palindrome number
22 is a palindrome number
54 is not a palindrome number

*/
===========================================
7)Generate prime numbers between 1 & given number100
/*
Prime Numbers Java Example
This Prime Numbers Java example shows how to generate prime numbers between 1 and given number using
for loop.
*/
public class GeneratePrimeNumbersExample {
    public static void main(String[] args) {
        //define limit
        int limit = 100;
        System.out.println("Prime numbers between 1 and " + limit);
        //loop through the numbers one by one
        for (int i = 1; i < 100; i++) {
            boolean isPrime = true;
            //check to see if the number is prime
            for (int j = 2; j < i; j++) {
                if (i % j == 0) {
                    isPrime = false;
                    break;
                }
            }
            // print the number
            if (isPrime)
                System.out.print(i + " ");
        }
    }
}

/*
Output of Prime Numbers example would be Prime numbers between 1 and 100

12357111317192329313741434753596167717379838997 */
=========================================
8)Pyramid of stars using nested for loops
/*
Java Pyramid 1 Example
This Java Pyramid example shows how to generate pyramid or triangle like given below using for loop.
*
**
***
****
*****
*/

public class JavaPyramid1 {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            for (int j = 0; j < i; j++) {
                System.out.print("*");
            }
            //generate a new line
            System.out.println("");
        }
    }

}

/*
Output of the above program would be

*
**
***
****
*****

*/
===========================
9)Reversed pyramid using for loops & decrement operator.
/*
Java Pyramid 5 Example
This Java Pyramid example shows how to generate pyramid or triangle like given below using for loop.
12345
1234
123
12
1
*/
public class JavaPyramid5 {
    public static void main(String[] args) {
        for (int i = 5; i > 0; i--) {
            for (int j = 0; j < i; j++) {
                System.out.print(j + 1);
            }
            System.out.println("");
        }
    }
}

/*     
    Output of the example would be
    12345
    1234
    123
    12
    1

*/
===========================================
10) Nested Switch
/*
Statements Example
This example shows how to use nested switch statements in a java program.
*/
public class NestedSwitchExample {
    public static void main(String[] args) {
        /*
        * Like any other Java statements, switch statements
        * can also be nested in each other as given in
        * below example.
        */
        int i = 0;
        int j = 1;
        switch (i)
        {
            case 0:
                switch (j)
                {
                    case 0:
                        System.out.println("i is 0, j is 0");
                        break;
                    case 1:
                        System.out.println("i is 0, j is 1");
                        break;
                    default:
                        System.out.println("nested default
                            case !!");
                        }
                        break;
                    default:
                        System.out.println("No matching case found!!");
                }

        }

    }

    /*
    Output would be,
    i is 0, j is 1

    */

====================================
11)Calculate Circle Area using radius
/*
This program shows how to calculate
*/

import java.io.BufferedReader;

import java.io.IOException;
import java.io.InputStreamReader;

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

int radius = 0;
System.out.println("Please enter radius of a circle");
//get the radius from console BufferedReader br = new BufferedReader(new
InputStreamReader(System.in));
radius = Integer.parseInt(br.readLine());
//if invalid value was entered catch(NumberFormatException ne)
{
System.out.println("Invalid radius value" + ne); System.exit(0);
}
catch(IOException ioe)
{
System.out.println("IO Error :" + ioe); System.exit(0);
}

/*
* Area of a circle is
* pi * r * r
* where r is a radius of a circle.
*/
//NOTE : use Math.PI constant to get value of pi double area = Math.PI * radius * radius;
System.out.println("Area of a circle is " + area);

}
}
/*
Output of Calculate Circle Area using Java Example would be  14
Please enter radius of a circle  19
Area of a circle is 1134.1149479459152

*/
====================================
12) Factorial of a number using recursion
/*
This program shows how to calculate
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class JavaFactorialUsingRecursion {

    public static void main(String args[]) throws NumberFormatException, IOException {
        System.out.println("Enter the number: ");
        //get input from the user
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int a = Integer.parseInt(br.readLine());
        //call the recursive function to generate factorial int result= fact(a);
    }
    System.out.println("Factorial of the number is: " + result);
}

static int fact(int b)
{
    if (b <= 1)
        //if the number is 1 then return 1
        return 1;
    //else call the same function with the value - 1 return b * fact(b-1);

}

/*
Output of this Java example would be
Enter the number:
5
Factorial of the number is: 120

*/
===========================================
13)Pyramid of numbers using for loops
/*
Generate Pyramid For a Given Number Example
This Java example shows how to generate a pyramid of numbers for given number using for loop example.
*/

import java.io.BufferedReader;
import java.io.InputStreamReader;
public class GeneratePyramidExample {
    public static void main(String[] args) throws Exception {
        BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter Number:");
        int as = Integer.parseInt(keyboard.readLine());
        System.out.println("Enter X:");
        int x = Integer.parseInt(keyboard.readLine());
        int y = 0;
        for (int i = 0; i <= as; i++) {
            for (int j = 1; j <= i; j++) {
                System.out.print(y + "\t");
                y = y + x;
            }
            System.out.println("");
        }
    }
}


/*
Output of this example would be
Enter Number:

5

Enter X:

1



0
1 2
3 4 5
6 7 8 9
10 11 12 13 14

----------------------------------------------
 17

Enter Number:

5

Enter X:

2



0
2 4
6 8 10
12 14 16 18
20 22 24 26 28
----------------------------------------------
Enter Number:

5

Enter X:

3



0
3 6
9 12 15
18 21 24 27
30 33 36 39 42

*/
======================================
14)To Find Maximum of Two Numbers.
/*
To Find Maximum of 2 Numbers using if else
*/

class Maxoftwo {
    public static void main(String args[]) { //taking value as command line argument. //Converting String format to Integer value int i = Integer.parseInt(args[0]);
        int j = Integer.parseInt(args[1]);
        if (i > j)
            System.out.println(i + " is greater than " + j);
        else
            System.out.println(j + " is greater than " + i);
    }


}

==========================================
15)To Find Minimum of Two Numbers using conditional operator
/*
To find minimum of 2 Numbers using ternary operator
*/

class Minoftwo {
    public static void main(String args[]) { //taking value as command line argument. //Converting String format to Integer value int i = Integer.parseInt(args[0]);
      int j = Integer.parseInt(args[1]);
        int result = (i < j) ? i : j;
        System.out.println(result + " is a minimum value");
    }


}
================================
16)Write a program that will read a float type value from the keyboard and print the following output.
->Small Integer not less than the number. ->Given Number.
->Largest Integer not greater than the number. 
/* Write a program that will read a float type value from the keyboard and print the following output.

->Small Integer not less than the number.

->Given Number.

->Largest Integer not greater than the number.

*/

class ValueFormat {
    public static void main(String args[]) {
            double i = 34.32; //given number
            System.out.println("Small Integer not greater than the number :
                    "+Math.ceil(i));
                    System.out.println("Given Number : " + i);
                    System.out.println("Largest Integer not greater than the number :
                        "+Math.floor(i));
                    }

}
=========================================
17)Write a program to generate 5 Random nos. between 1 to 100, and it should not follow with decimal point.

class RandomDemo {
    public static void main(String args[]) {
        for (int i = 1; i <= 5; i++) {
         System.out.println((int)(Math.random() * 100));
        }

    }

}
=============================
18) Write a program to display a greet message according to Marks obtained by student
class SwitchDemo {

    public static void main(String args[]) {

        int marks = Integer.parseInt(args[0]); //take marks as command line argument.
        switch (marks / 10) {

            case 10:

            case 9:

            case 8:

                System.out.println("Excellent");

                break;

            case 7:

                System.out.println("Very Good");

                break;

            case 6:

                System.out.println("Good");

                break;

            case 5:

                System.out.println("Work Hard");

                break;

            case 4:

                System.out.println("Poor");

                break;

            case 3:

            case 2:

            case 1:

            case 0:

                System.out.println("Very Poor");

                break;

            default:

                System.out.println("Invalid value Entered");

        }

    }


}

=================================
19)Write a program to find SUM AND PRODUCT of a given Digit.

class Sum_Product_ofDigit {
    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        //taking value as command line argument.
        int temp = num, result = 0;
        //Logic for sum of digit
        while (temp > 0) {
            result = result + temp;
            temp--;
        }
        System.out.println("Sum of Digit for " + num + " is : " + result);
        //Logic for product of digit
        temp = num;
        result = 1;
        while (temp > 0) {
            result = result * temp;
            temp--;
        }
        System.out.println("Product of Digit for " + num + " is : " + result);
    }


}
=================================
20)Write a program to find sum of all integers greater than 100 and less than 200 that are divisible by 7

class SumOfDigit {
    public static void main(String args[]) {
        int result = 0;
        for (int i = 100; i <= 200; i++) {
            if (i % 7 == 0)
                result += i;
        }
        System.out.println("Output of Program is : " + result);
    }

}

=====================================
21)Write a program to concatenate string using for Loop
/* Write a program to concatenate string using for Loop
Example:
Input - 5

24
Output - 1 2 3 4 5 */

class Join {

    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        String result = " ";
        for (int i = 1; i <= num; i++) {
            result = result + i + " ";
        }
        System.out.println(result);
    }

}
===================================
22) Program to Display Multiplication Table
class MultiplicationTable {
    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        System.out.println("*****MULTIPLICATION TABLE*****");
        for (int i = 1; i <= num; i++) {
            for (int j = 1; j <= num; j++) {
                System.out.print(" " + i * j + " ");
            }
            System.out.print("\n");
        }
    }

}
==================================
23)Write a program to Swap the values
class Swap {
    public static void main(String args[]) {
        int num1 = Integer.parseInt(args[0]);
        int num2 = Integer.parseInt(args[1]);
        System.out.println("\n***Before Swapping***");
        System.out.println("Number 1 : " + num1);
        System.out.println("Number 2 : " + num2); //Swap logic
        num1 = num1 + num2;
        num2 = num1 - num2;
        num1 = num1 - num2;
        System.out.println("\n***After Swapping***");
        System.out.println("Number 1 : " + num1);
        System.out.println("Number 2 : " + num2);
    }

}
================================
24)Write a program to convert given no. of days into months and days.(Assume that each month is of 30 days)
/*Program 24 - Write a program to convert given no. of days into months and days.(Assume that each month is of 30 days)

Example :

Input - 69

Output - 69 days = 2 Month and 9 days */

class DayMonthDemo {
    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        int days = num % 30;
        int month = num / 30;
        System.out.println(num + " days = " + month + " Month and " + days + " days");
    }

}
====================================
25) Write a program to Display Invert Triangle using while loop.
/*Program 25 - Write a program to Display Invert Triangle using while loop.

Example:
Input - 5

Output :

55555
4444
3 3 3
2 2
1


27
*/

class InvertTriangle {
    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        while (num > 0) {
            for (int j = 1; j <= num; j++) {
                System.out.print(" " + num + " ");
            }
            System.out.print("\n");
            num--;
        }
    }

}
=================================
26)Write a program to find whether given no. is Armstrong or not.
/*Program 26 - Write a program to find whether given no.
is Armstrong or not.

Example :

Input - 153

Output - 1^3 + 5^3 + 3^3 = 153, so it is Armstrong no. */

class Armstrong {
    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        int n = num; //use to check at last time int check=0,remainder; while(num > 0){
        remainder = num % 10;
        check = check + (int) Math.pow(remainder, 3);
        num = num / 10;
    }
    if (check == n)
        System.out.println(n + " is an Armstrong Number");
    else
        System.out.println(n + " is not a Armstrong Number");
}

}
=================================
27)switch case demo
/*Program 27 - switch case demo
Example :
Input - 124

Output - One Two Four */
class SwitchCaseDemo {
    public static void main(String args[]) {
        try {
            int num = Integer.parseInt(args[0]);
            int n = num; //used at last time check
            int reverse = 0, remainder;
            while (num > 0) {
                remainder = num % 10;
                reverse = reverse * 10 + remainder;
                num = num / 10;
            }
            String result = ""; //contains the actual output while(reverse > 0){
            remainder = reverse % 10;
            reverse = reverse / 10;
            switch (remainder) {
                case 0:
                    result = result + "Zero ";
                    break;
                case 1:
                    result = result + "One ";
                    break;
                case 2:
                    result = result + "Two ";
                    break;
                case 3:
                    result = result + "Three ";
                    break;
                case 4:
                    result = result + "Four ";
                    break;
                case 5:
                    result = result + "Five ";
                    break;
                case 6:
                    result = result + "Six ";
                    break;
                case 7:
                    result = result + "Seven ";
                    break;
                case 8:
                    result = result + "Eight ";
                    break;
                case 9:
                    result = result + "Nine ";
                    break;
                default:
                    result = "";
            }

        }
        System.out.println(result);
    } catch (Exception e) {
        System.out.println("Invalid Number Format");
    }
}

}
===============================
28) Write a program to generate Harmonic Series.
/*Program 28 - Write a program to generate Harmonic Series.

Example :

Input - 5

Output - 1 + 1/2 + 1/3 + 1/4 + 1/5 = 2.28 (Approximately) */

class HarmonicSeries {
    public static void main(String args[]) {
        int num = Integer.parseInt(args[0]);
        double result = 0.0;
        while (num > 0) {
            result = result + (double) 1 / num;
            num--;
        }
        System.out.println("Output of Harmonic Series is " + result);
    }


}
============================
29)  Write a program to find average of consecutive N Odd numbers and even numbers.
//Program 29 - Write a program to find average of consecutive N Odd no. and Even no.
class EvenOdd_Avg {
    public static void main(String args[]) {
        int n = Integer.parseInt(args[0]);
        int cntEven = 0, cntOdd = 0, sumEven = 0, sumOdd = 0;
        while (n > 0) {
            if (n % 2 == 0) {
                cntEven++;
                sumEven = sumEven + n;
            } else {
                cntOdd++;
                sumOdd = sumOdd + n;
            }
            n--;
        }
        int evenAvg, oddAvg;
        evenAvg = sumEven / cntEven;
        oddAvg = sumOdd / cntOdd;
        System.out.println("Average of first N Even no is " + evenAvg);
        System.out.println("Average of first N Odd no is " + oddAvg);
    }

}
=============================
30) Display Triangle as follow: (using for loops)
1
2 3
4 5 6
78910...N*/
/*Program 30 - Display Triangle as follow.
1
2 3
4 5 6
78910...N 
* /
class Output1 {
    public static void main(String args[]) {
        int c = 0;
        int n = Integer.parseInt(args[0]);
        loop1: for (int i = 1; i <= n; i++) {
            loop2: for (int j = 1; j <= i; j++) {
                if (c != n) {
                    c++;
                    System.out.print(c + " ");
                } else
                    break loop1;
            }
            System.out.print("\n");
          }
    }

}