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Here's how to check for Happy Numbers in Java using the HashSet method along with the <a href="https://www.tutorialsfreak.com/java-tutorial/java-loops" target="_blank" rel="noopener">while loop</a>:

Happy Number Program in Java Using while loop and HashSet

A happy number is a special type of number that, when you repeatedly square its digits and add them together, eventually equals 1. If this process doesn't reach 1 and instead goes into an endless loop, the number is not a happy number.
Let us understand it with an example using the number 19:
<ul>
<li dir="ltr" aria-level="1">
Start with the number 19.
</li>
<li dir="ltr" aria-level="1">
Square each digit and add them together: 1^2 + 9^2 = 1 + 81 = 82.
</li>
</ul>
Now, repeat the process with the result, 82:
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<li dir="ltr" aria-level="1">
Square each digit and add them together: 8^2 + 2^2 = 64 + 4 = 68.
</li>
<li dir="ltr" aria-level="1">
Repeat again: 6^2 + 8^2 = 36 + 64 = 100.
</li>
<li dir="ltr" aria-level="1">
Once more: 1^2 + 0^2 + 0^2 = 1 + 0 + 0 = 1.
</li>
</ul>
After a few iterations, we reach 1, so 19 is a happy number.
Not all numbers are happy numbers.&nbsp;
For example, if we start with 4:
<ul>
<li dir="ltr" aria-level="1">
Start with the number 4.
</li>
<li dir="ltr" aria-level="1">
Square each digit and add them together: 4^2 = 16.
</li>
<li dir="ltr" aria-level="1">
Repeat: 1^2 + 6^2 = 1 + 36 = 37.
</li>
<li dir="ltr" aria-level="1">
Repeat: 3^2 + 7^2 = 9 + 49 = 58.
</li>
<li dir="ltr" aria-level="1">
Repeat: 5^2 + 8^2 = 25 + 64 = 89.
</li>
<li dir="ltr" aria-level="1">
Repeat: 8^2 + 9^2 = 64 + 81 = 145.
</li>
<li dir="ltr" aria-level="1">
Repeat: 1^2 + 4^2 + 5^2 = 1 + 16 + 25 = 42.
</li>
<li dir="ltr" aria-level="1">
Repeat: 4^2 + 2^2 = 16 + 4 = 20.
</li>
<li dir="ltr" aria-level="1">
Repeat: 2^2 + 0^2 = 4 + 0 = 4.
</li>
</ul>
The process keeps cycling between 4 and 20, never reaching 1. So, 4 is not a happy number.&nbsp;
In this tutorial, we will learn how to check Happy Number in Java using different approaches, methods, and examples.&nbsp;

Happy Number in Java (Easy Programs With Logic)

Here's how to check for Happy Number in Java using the Floyd's Cycle Detection Algorithm (Tortoise and Hare method):

Check Happy Number in Java Using Floyd Algorithm

Here's how to check for Happy Numbers in Java using <a href="https://www.tutorialsfreak.com/java-tutorial/java-recursion" target="_blank" rel="noopener">recursion</a>:

Happy Number Program in Java Using Recursion

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Learn how to check if a number is a happy number in Java with this easy program. Get Started with a simple way to calculate Happy Numbers with logic.