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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.

  1. Read or initialize a number (num).
  2. Add 1 to the given number i.e. num+1.
  3. Find the square root of num+1.
  4. 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

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.


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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