How to check if a number is Strong's number in Java?

A number is called a Strontio number and if we multiply 2 with a four-digit number, the tens and hundreds digits of the resulting number are the same.

To put it simply, a Strontio number is basically a four-digit number. When we multiply by 2, the result is a number with exactly the same tens and hundreds digits.

Some examples of Strontio numbers include - 1111, 2222, 3333, 4444, 5555, 6666, 7777, 8888, 9999, 1001...etc.

In this article, we will learn how to check if a number is strong using Java programming language.

Show you some examples

Example 1

The input number is 1111.

Let’s check it out using the logic of Strontio numbers.

Multiply the given number by 2= 1111 * 2 = 2222.

As we noticed here, the resulting numbers in hundreds and tens are the same.

Therefore, 1111 is a Strontio number.

Example 2

The input number is 7777.

Let’s check it out using the logic of Strontio numbers.

Multiply the given number by 2= 7777 * 2 = 15554.

As we noticed here, the resulting numbers in hundreds and tens are the same.

Therefore, 7777 is a Strontio number.

Example 3

The input number is 1234.

Let’s check it out using the logic of Strontio numbers.

Multiply the given number by 2= 1234 * 2 = 2468.

As we noticed here, the resulting numbers in hundreds and tens are not the same.

Therefore, 1234 is not a Strontio number.

algorithm

Step 1 - Get the four-digit input number via static input or user input.

Step 2 - Multiply the input number by 2 and remove all digits except the hundreds and tens digits from the resulting number.

Step 3 - Now we have a two digit number, so we check if the two digits of the number are the same.

Step 4 - If both numbers are the same, the number entered is called a Strontio number, otherwise it is not.

Multiple methods

We provide solutions in different ways.

• By using static input values

• By using user input value

• By user-defined method

Let’s look at the program and its output one by one.

Method 1: Using static input values

In this method we declare a variable with a static input value and then by using an algorithm we can check if the number is a Strontio number.

Example

import java.util.*;
public class Main {
   public static void main(String args[]) {
      
      //declare a variable and store a number to it by static input method
      int inputNumber=9999;
      
      //declare a variable to store the input value temporarily
      int temp=inputNumber;
      
      //remove all the digits excluding hundreds and tens place digit
      inputNumber=(inputNumber*2%1000)/10;
      
      //Now compare hundreds place value with tens place value
      if(inputNumber%10==inputNumber/10)
         
         //if true
         System.out.println(temp+ " is a strontio number.");
      else
         
         //if false
         System.out.println(temp+ " is not a strontio number.");
   }
}

Output

9999 is a strontio number.

Method 2: Using user input values

In this method we take a four digit number as user input and then by using an algorithm we can check if the number is a Strontio number.

Example

import java.util.*;
public class Main {
   public static void main(String args[]) {
      
      //create object of Scanner Class
      Scanner sc=new Scanner(System.in);
      
      //Ask the user to enter a four digit number
      System.out.print("Enter a four digit number: ");
      
      //Declare a variable and store the collected number
       int inputNumber=sc.nextInt();
      
      //declare a variable to store the input value temporarily
      int temp=inputNumber;
      
      //remove all the digits excluding hundreds and tens place digit
      inputNumber=(inputNumber*2%1000)/10;
      
      //Now compare hundreds place value with tens place value
      if(inputNumber%10==inputNumber/10)
         
         //if true
         System.out.println(temp+ " is a strontio number.");
      else
        
        //if false
         System.out.println(temp+ " is not a strontio number.");
   } 
}

Output

Enter a four digit number: 2222
2222 is a strontio number.

Method 3: Using user-defined methods

In this method, a four digit number is taken as a static input and the number is passed as a parameter to the user defined method and then using an algorithm inside the method we can check if the number is a Strontio number.

Example

import java.util.*;
public class Main {
   
   //main method
   public static void main(String args[]) {
      
      //declare a variable and store a number to it by static input method
      int inputNumber=3333;
      
      //call the user-defined method to check the strontio number
      if(checkStrontio(inputNumber))
         
         //print if condition true
         System.out.println(inputNumber+ " is a strontio number.");
      else
         
         //print if condition false
         System.out.println(inputNumber+ " is not a strontio number.");
   }

   //user-defined method to check the strontio number
   static boolean checkStrontio(int n) {
      
      //declare a variable to store the input value temporarily
      int temp=n;
      
      //remove all the digits excluding hundreds and tens place digit
      n=(n*2%1000)/10;
      
      //Now compare hundreds place value with tens place value
      if(n%10==n/10)
         
         //if true
         return true;
      else
         
         //if false
         return false;
   }
}

Output

3333 is a strontio number.

In this article, we explored how to check if a number is a Strontio number in Java using different methods.

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