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In this tutorial of Emirp Number in Java, we will write a program to check for the Emirp number in Java. Let us start by understanding, what is Emirp number.

Emirp Number

A number is said to be an Emirp number if it is a prime number and when reversed, the result formed is also a Prime Number. Emirp is backward for Prime, which indicates that a number, when formed backward, is also a prime number. Hence also known as twisted prime numbers.

Example: 13, 79, 199, 107 etc.

Explanation: Consider a Prime Number, 13
The reverse of 13: 31, which is also a prime number. Therefore, 13 is an Emirp Number.

Java Program to check for Emirp Number Using Function.

import java.io.*;
import java.util.*;

public class EmirpNumber
{
   //function to check for prime, returns boolean
   public static boolean isPrime(int n)
   {
      if (n <= 1)
         return false;

      for (int i = 2; i < n; i++)
      {
         if (n % i == 0)
            return false;
      }

      return true;
   }

   //function to check for emirp number, returns boolean
   public static boolean isEmirp(int n)
   {
      //calls isPrime function and checks for prime
      if (isPrime(n) == false)
         return false;

      int rev = 0;
      while (n != 0)
      {
         int digit = n % 10;
         rev = rev *10 + digit;

         n = n / 10;
      }

      //after reverse again checks for prime  
      return isPrime(rev);
   }

   //main function
   public static void main(String args[])
   {
      Scanner sc = new Scanner(System.in);

      System.out.print("Enter a number: ");
      int n = sc.nextInt();

      //Display accordingly
      if (isEmirp(n) == true)
         System.out.println(n + " is an Emirp number.");
      else
         System.out.println(n + " is not an Emirp number.");
   }
}

Output:

//First Run
Enter a number: 13
13 is an Emirp number.

//Second Run
Enter a number: 107
107 is an Emirp number.

//Third Run
Enter a number: 23
23 is not an Emirp number.

In this tutorial, we will write an Autobiographical Number Program in Java and also learn what is Autobiographical Number.

Autobiographical Number

An autobiographical number is a number such that the first digit of it counts how many zeroes are there in it, the second digit counts how many ones are there, and so on. Basically, it counts the frequency of digits from 0 to 9 in order which they occur in a number.

Example: 1210 has 1 zero, 2 ones, 1 two, and 0 threes.
Some other examples include 2020, 21200, 3211000, 42101000, etc.

Explanation: Consider a number, 21200.

First, the sum of the digits: 2+1+2+0+0 = 5
Second, count the number of digits: 5
Since the sum of the digits is equal to the number of digits present in a number. Therefore, 21200 is an autobiographical number.

Java Program to check if the given number is Autobiographical Number or not

import java.util.*;

public class AutobiographicalNumber
{
   public static void main(String args[])
   {
      int num, n;
      String str;
      boolean flag;
      Scanner sc = new Scanner(System.in);
      
      System.out.print("Enter the number: ");
      num = sc.nextInt();
      
      num = Math.abs(num);
      n = num;
      
      str = String.valueOf(num);

      int digitarray[] = new int[str.length()];
      for (int i = digitarray.length - 1; i >= 0; i--)
      {
         digitarray[i] = n % 10;
         n = n / 10;
      }

      flag = true;
      
      for (int i = 0; i < digitarray.length; i++)
      {
         int count = 0;
         for (int j = 0; j < digitarray.length; j++)
         {
            if (i == digitarray[j])
               count++;
         }

         if (count != digitarray[i])
         {
            flag = false;
            break;
         }
      }

      if (flag)
         System.out.println(num + " is an Autobiographical number.");
      else
         System.out.println(num + " is not an Autobiographical number.");
   }
}

Output:

//First Run
Enter the number: 1210
1210 is an Autobiographical number.

\\Second Run
Enter the number: 1410
1410 is not an Autobiographical number.

In this tutorial, we will write an ATM program in Java. The program will represent the ATM transaction executed.

Operation available in the ATM Transaction are:

1. Withdraw
2. Deposit
3. Check Balance
4. Exit

The user will choose one of the above operations:

• Withdraw is to withdraw the amount from an ATM. The user is asked to enter the amount and after the withdrawal process is complete, we need to remove that amount from the total balance.
• Deposit is to add an amount to the total balance, here also the user enters the amount to be added to the total balance.
• Check Balance means simply display the total balance available in the user’s account.
• Exit is to return the user to the main page from the current transaction mode. For that, we will use exit(0).

ATM program Java

The following program uses the switch statement in java to create a case for each transaction or option.

import java.util.Scanner;

public class ATMProgram
{
  public static void main(String args[])
  {
    int balance = 5000, withdraw, deposit;
    Scanner sc = new Scanner(System.in);

    while (true)
    {
      System.out.println("ATM (Automated Teller Machine)");
      System.out.println("Choose 1 for Withdraw");
      System.out.println("Choose 2 for Deposit");
      System.out.println("Choose 3 for Check Balance");
      System.out.println("Choose 4 for EXIT");
      System.out.print("Choose the operation you want to perform: ");

      //user choice input 
      int choice = sc.nextInt();
      switch (choice)
      {
        case 1:
          System.out.print("Enter the amount to be withdrawn: ");
          withdraw = sc.nextInt();

          //balance need to be with the withdrawn amount  
          if (balance >= withdraw)  //for successful transaction 
          {
            balance = balance - withdraw;
            System.out.println("Withdrawal successful! Please collect your money.");
          }
          else	//not enough balance
          {
            System.out.println("Insufficient Balance");
          }

          System.out.println("");
          break;

        case 2:
          System.out.print("Enter amount to be deposited: ");
          deposit = sc.nextInt();

          //adding to the total balance 
          balance = balance + deposit;
          System.out.println("Your Money has been successfully depsited:");
          System.out.println("");
          break;

        case 3:
          //balance check 
          System.out.println("Available Balance: " + balance);
          System.out.println("");
          break;

        case 4:
          //for exit 
          System.out.println("Successfully EXIT.");
          System.exit(0);
      }
    }
  }
}

Output:

In this tutorial, we will write java programs to check for Spy Numbers. We will look at two different java programs son Spy Number

1. Java Program to Check If a Number is Spy number or not.
2. Java Program to print all the Spy Number within a given Range.

What is Spy Number?

A number is said to be a spy number if the sum of all its digits is equal to the product of all its digits.
Example:

Number: 123 
Sum of its digits: 1+2+3 = 6
Product of its digits: 1*2*3 = 6  
Sum and Product are equal, hence, 123 is a Spy number.

Similarly, you may check for other numbers such as 22, 132, 1124, etc.

Spy Number in Java Program

1. Java Program to Check If a Number is Spy number or not

import java.util.Scanner;

public class SpyNumber
{
   public static void main(String args[])
   {
      int num, product = 1, sum = 0, lastdigit;
      Scanner sc = new Scanner(System.in);

      //read from user
      System.out.print("Enter the number: ");
      num = sc.nextInt();

      int number = num;

      //calculation for sum and product 
      while (num > 0)
      {
         lastdigit = num % 10;

        	//calculating sum
         sum = sum + lastdigit;
        	//calculating product
         product = product * lastdigit;

         num = num / 10;
      }

      //compares the sum and product and print the result
      if (sum == product)
         System.out.println(number + " is a spy number.");
      else
         System.out.println(number + " not a spy number.");
   }
}

Output:

//First Run
Enter the number: 1124
1124 is a spy number.

//Second Run
Enter the number: 166
166 not a spy number.

2. Java Program to print all the Spy Number within a given Range.

We will create a separate Boolean function (isSpyNumber()) that will return true if the sum of the digits and the product of the digits are equal else will return false and print them accordingly.

The program takes the input for the lower range and upper range value and will pass those numbers between this range to the function as an argument.

import java.util.Scanner;

public class SpyNumber
{
   private static boolean isSpyNumber(int number)
   {
      int lastdigit = 0;
      int sum = 0, product = 1;

      //calculation  
      while (number != 0)
      {
         lastdigit = number % 10;

        	//calculating sum
         sum = sum + lastdigit;
        	//calculating product
         product = product * lastdigit;

         number = number / 10;
      }

      //comapre and return true value if found equal  
      if (sum == product)
         return true;

      return false;
   }

   public static void main(String args[])
   {
      int lwRange, upRange;
      Scanner sc = new Scanner(System.in);

      //read from user
      System.out.print("Enter the Lower Range: ");
      lwRange = sc.nextInt();
      System.out.print("Enter the Upper Range: ");
      upRange = sc.nextInt();

      System.out.println("The Spy numbers between " + lwRange + " and " + upRange + " are: ");
      for (int i = lwRange; i <= upRange; i++)
      {
         //calling function at each iteration, that is for each number within the range
         if (isSpyNumber(i))
            System.out.print(i + " ");
      }
   }
}

Output:

Enter the Lower Range: 1
Enter the Upper Range: 1000
The Spy numbers between 1 and 1000 are:
1 2 3 4 5 6 7 8 9 22 123 132 213 231 312 321