Answer 1

For example : input 5

First one don't work as it has infinite loop.
number--; must be inside loop. The it prints 5*4, 4*3, 3*2, 2*1

Second , find 5*4*3*2*1 = 120

Answer 2

JavaTpoint
Geekforgreeks
TutorialPoint
Stackoverflow
Javarevisted

HowToDoItInJava
And mainly oracle documentation..

https://howtodoinjava.com/resources/best-way-to-learn-java/