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Vishal Arora
Greenhorn

Joined: Jul 29, 2005
Posts: 9
I got this question given below from a mock exam and i m not able to understand its output.Can somebody explain why its output will be "false true false true".
import java.io.*;

public class T026
{

public static void main(String args[])
{
System.out.print((1 - 1 / 3 * 3 ==0)+" "); //1

System.out.print((1 - 1.0f / 3.0f * 3.0f==0)+" "); //2

System.out.print((1 - 1.0f / 3.0f * 3.0d==0)+" "); //3

System.out.print((1 - 1.0d / 3.0d * 3.0d==0)+" "); //4
}
}
Sherry Jacob
Ranch Hand

Joined: Jun 29, 2005
Posts: 128
Hi,
Here are the answers to ur queries:
The first statement,
1 - 1 / 3 * 3
will be evaluated as follows:
1 - (1/3) * 3 = 1 - (0 * 3) = 1 - 0 = 1.
This is because in integer arithmetic operations, the division operator (/) has highest precedence followed by the multiplication operator (*) followed by Addition and Subtraction. Hence //1 returns false.

1 - 1.0f / 3.0f * 3.0f

Again, the evaluation proceeds as 1 - (1.0f / 3.0f) * 3.0f = 1 - (0.3333333... * 3) = 1 - 1 = 0. Thus //2 returns true.

1 - 1.0f / 3.0f * 3.0d

The evaluation proceeds as 1 - (1.0f / 3.0f) * 3.0d. But here we have a floating point and a double value. So the floating point operation is performed first...then converted to double...1 - 0.33333d * 3.0d. But converting from floating point to double causes some loss of precision and hence the result is <> 0. Hence //3 returns false.

Finally,
1 - 1.0d / 3.0d * 3.0d

returns true as all operations are with double values. Reasoning is much the same as at //2

Hope u got ur answers ?

Correct me if I was wrong anywhere.


<strong><br />Cheers !!<br /> <br />Sherry<br /></strong><br />[SCJP 1.4]
 
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