Sunny Number in Java

In this section, we will learn what is sunny numbers and how to create a Java program to find the sunny numbers. We will also create a Java program to find all the sunny numbers between the specified range.

Sunny Number

A number is called a sunny number if the number next to the given number is a perfect square. In other words, a number N will be a sunny number if N+1 is a perfect square.

Let's understand it through an example.

Sunny Number Example

Suppose, we have to check if 80 is a sunny number or not.

Given, N=80 then N+1 will be 80+1=81, which is a perfect square of the number 9. Hence 80 is a sunny number.

Let's take another number 10.

Given, N=10 then N+1 will be 10+1=11, which is not a perfect square. Hence 10 is not a sunny number.

Steps to Find Sunny Number

The logic is very simple. To find the sunny number, we need only to check whether N+1 is the perfect square or not.

Read or initialize a number (num).
Add 1 to the given number i.e. num+1.
Find the square root of num+1.
If the square root is an integer, the given number is sunny, else not a sunny number.

Let's implement the above steps in a Java program.

Sunny Number Java Program

SunnyNumberExample1.java

import java.util.*; 
public class SunnyNumberExample1
{ 
//driver code 
public static void main(String args[]) 
{ 
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number to check: ");
//reading a number from the user
int N=sc.nextInt();
//calling user-defined function 
isSunnyNumber(N); 
}     
//function checks whether the given is a perfect square or not 
static boolean findPerfectSquare(double num) 
{ 
//finds the square root of the ggiven number
double square_root = Math.sqrt(num); 
//if square root is an integer 
return((square_root - Math.floor(square_root)) == 0); 
} 
//function that checks whether the given number is Sunny or not
static void isSunnyNumber(int N) 
{ 
//checks N+1 is perfect square or not
if (findPerfectSquare(N + 1)) 
{ 
System.out.println("The given number is a sunny number."); 
} 
//executes if N+1 is not a perfect square
else
{ 
System.out.println("The given number is not a sunny number."); 
} 
} 
}

Output 1:

Enter a number to check: 80
The given number is a sunny number.

Output 2:

Enter a number to check: 670
The given number is not a sunny number.

Let's create another Java program and find all the sunny numbers between a given range.

SunnyNumberExample2.java

import java.util.Scanner;
public class SunnyNumberExample2
{
//user-defined function that determines all the sunny numbers
public static boolean isSunnyNumber(int number) 
{
//determines the square root of number+1 using Math.sqrt() method
if(Math.sqrt(number+1)%1 == 0)
return true;
else 
return false;
}
//driver code
public static void main(String args[]) 
{
//lr is lower range and ur is upper range
int lr = 0, ur = 0;
Scanner scan = new Scanner(System.in);
System.out.print("Enter lower range: ");
//reads an integer (lr) from the user
lr = scan.nextInt();
System.out.print("Enter upper range: ");
//reads an integer (ur) from the user
ur = scan.nextInt();
System.out.println("The Sunny number from "+ lr + " to "+ ur+" are: ");
for(int i=lr; i<=ur; i++) 
{
//calling user-defined number
if(isSunny(i))
System.out.print(i +" ");
}
}
}

Output:

Enter lower range: 1
Enter upper range: 1000
The Sunny number from 1 to 1000 are: 
3 8 15 24 35 48 63 80 99 120 143 168 195 224 255 288 323 360 399 440 483 528 575 624 675 728 783 840 899 960

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