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# Math.round() method

shetal bansal
Ranch Hand

Joined: May 09, 2005
Posts: 63
What is the output of following

Round f4 is -5
Round f5 is 6
Round f6 is -5
Round f7 is 5

How r the value of f6 and f7 getting calculated??
marc weber
Sheriff

Joined: Aug 31, 2004
Posts: 11343

Math.round(double d)...

"Returns the closest long to the argument. The result is rounded to an integer by adding 1/2, taking the floor of the result, and casting the result to type long."

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Math.html

"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer
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Abdulla Mamuwala
Ranch Hand

Joined: Jan 09, 2004
Posts: 225
I am not sure, but this could be the way you do it.
First add 0.5 to the argument and than perform a Math.floor() on it.

Here f6=-5.49
-5.49 + 0.5 = -4.99
Now, we perform a Math.floor() on -4.99 giving -5, because -5 is less than -4.

Similarly f7=5.49
5.49 + 0.5 = 5.99
Now, we perform a Math.floor() on 5.99 giving 5, because 5 is less than 6.

Math.round() returns integer closest to the argument in the case above because the arguments are of type float.
[ June 17, 2005: Message edited by: Abdulla Mamuwala ]
Edwin Dalorzo
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Joined: Dec 31, 2004
Posts: 961
For the SCJP exam I think it is important to recognize the next things

• double Math.floor(double a): receives a double and returns a double
• double Math.ceil(double a) : receives a double and returns a double
• int Math.round(float a): receives a float returns a integer
• long Math.round(double a): receives a double returns a long

• It is important to recognize that in the next output

Now, rouund might behave different for positive and negative numbers.

However:

Be careful with that, because that is a probable question in the exam.
Rick O'Shay
Ranch Hand

Joined: Sep 19, 2004
Posts: 531
float f6 = -5.49f;
float f7 = 5.49f;

Rounds off to the nearest integer: -5 and 5 respectively.

Given -5.5 and 5.5 you need a rounding rule since there are two "nearest" integers. They decided to round up: -5, 6 respectively. In other words if smack dab in the middle add 0.5.
shetal bansal
Ranch Hand

Joined: May 09, 2005
Posts: 63
Thanxs a lot for the wonderful replies!!

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subject: Math.round() method