1134. Armstrong Number:

The Essence: The question tries to teach us:

• Splitting a number into individual digits.
• Finding the length of a number.

Details:

• We can split a number into individual digits in a while loop, getting the last digit with modulo sign (%) and dividing the number by 10.
• We can find the length of a number, simply covering it to a String and calling the "length()" function.

(There is also a mathematical method to find the length: int length = (int) Math.log10(n) + 1;)