k&b doubt 2

[amit taneja]

hi in chapter 6...

in one question...


Given the following,
1. public class Example {
2. public static void main(String [] args) {
3. double values[] = {-2.3, -1.0, 0.25, 4};
4. int cnt = 0;
5. for (int x=0; x < values.length; x++) {
6. if (Math.round(values[x] + .5) == Math.ceil(values[x])) {
7. ++cnt;
8. }
9. }
10. System.out.println("same results " + cnt + " time(s)");
11. }
12. }
what is the result?
A. same results 0 time(s)
B. same results 2 time(s)
C. same results 4 time(s)
D. Compilation fails.
E. An exception is thrown at runtime.


its anser is "B"

but don't understand why... i am not able to understand its explaination...
kindly clear the doubt...

thanx

[Srinivasa Raghavan]

Try to run this code.

  public class example {
 public static void main(String [] args) {
 double values[] = {-2.3, -1.0, 0.25, 4};
 int cnt = 0;
 for (int x=0; x < values.length; x++) {
 if (Math.round(values[x] + .5) == Math.ceil(values[x])) {
System.out.println ( " values[x] : " + values[x] + 
" Math.round(values[x] + .5) " + Math.round(values[x] + .5) + 
" Math.ceil(values[x]) " + Math.ceil(values[x]) );
 ++cnt;
 }
 }
 System.out.println("same results " + cnt + " time(s)");
 }
 } 

[ May 10, 2005: Message edited by: Srinivasa Raghavan ]

[alzamabar]

Originally posted by amit taneja:
hi in chapter 6...

in one question...


Given the following,
1. public class Example {
2. public static void main(String [] args) {
3. double values[] = {-2.3, -1.0, 0.25, 4};
4. int cnt = 0;
5. for (int x=0; x < values.length; x++) {
6. if (Math.round(values[x] + .5) == Math.ceil(values[x])) {
7. ++cnt;
8. }
9. }
10. System.out.println("same results " + cnt + " time(s)");
11. }
12. }
what is the result?
A. same results 0 time(s)
B. same results 2 time(s)
C. same results 4 time(s)
D. Compilation fails.
E. An exception is thrown at runtime.


its anser is "B"

but don't understand why... i am not able to understand its explaination...
kindly clear the doubt...

thanx

The logic is as follows:

-2.3 and 0.25 are the correct answers.

For -2.3:

(-2.3 + .5) == -1.7
-1.7 Rounded == -2.0

-2.3 Ceiled == -2

Therefore -2.0 == 2


For 0.25:

(0.25 + .5) == 0.75
0.75 Rounded == 1.0

0.25 Ceiled == 1

Therefore 1.0 == 1


-1.0 is not correct because:

(-1.0 + .5) == -.5
-.5 Rounded == 0

-1.0 Ceiled == -1.0

Therefore 0 != -1.0


4 Is incorrect because:

(4 + .5) == 4.5
4.5 Rounded == 5

4 Ceiled == 4

Therefore 4 != 5

[Srinivasa Raghavan]

Therefore -2.0 == 2

It should be -2.0 == -2.0

[alzamabar]

Originally posted by Srinivasa Raghavan:

It should be -2.0 == -2.0

No, it should be -2.0 == 2

From Java Language Specification (chapter 5.6.2):

If either operand is of type double, the other is converted to double.

Therefore 2 is promoted to be 2.0 and the two results are equal.

You can run the following code for testing:

boolean isEqual = (2.0D == 2);
System.out.println(isEqual);
 

[Srinivasa Raghavan]

Yep i agree this

If either operand is of type double, the other is converted to double.

But it should be negative right or am i going wrong any where ?
I mean -2.0 == -2
[ May 10, 2005: Message edited by: Srinivasa Raghavan ]

[amit taneja]

thanx
[ May 10, 2005: Message edited by: amit taneja ]

[alzamabar]

Originally posted by Srinivasa Raghavan:
Yep i agree this

If either operand is of type double, the other is converted to double.

But it should be negative right or am i going wrong any where ?
I mean -2.0 == -2

[ May 10, 2005: Message edited by: Srinivasa Raghavan ]

Yes it should be negative. Sorry for the typo