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Confusion in random() function

Shivani Prajapati

Joined: Aug 23, 2006
Posts: 9
What will be the result of the expression ((int) (Math.random()*4))

Answer in khalid mughal book is � �expression will evaluate to one of the numbers 0,1,2 or 3.�
But how can it be possible?
Paras Jain
Ranch Hand

Joined: Feb 26, 2005
Posts: 137
As per the API random function "Returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0. Returned values are chosen pseudorandomly with (approximately) uniform distribution from that range."
That means you will get something between 0 and 1(non-inclusive) like 0.1, 0.2,.03 .... 0.999. Any number within this range when multiplied by 4 wil give values between 0 to 4 like
.1*4 = .4 ,
.6*4 = 2.4 .....
.999*4 = 3.996.

Hope you got the point.

Paras Jain
SCJP 5.0
Paras Jain
Ranch Hand

Joined: Feb 26, 2005
Posts: 137
And I forgot to mention that when these numbers will be casted to (int) the values after decimal will be lost
.1*4 = .4 which becomes 0,
.6*4 = 2.4 which becomes 2.....
.999*4 = 3.996 which becomes 3
Consider Paul's rocket mass heater.
subject: Confusion in random() function