K&B chapter 7-Question 6 (SCJP 1.4)

[Sandip Kaviman]

Can anyone please explain this. I am little confused with Math.round(values[x]+.5), as Math.round() does not take any argument, it is explained in answers but still it is not clear to me.

 
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]))){
++cnt;
}
        }
System.out.println("Same results "+cnt+" times(s)");
   }
}   

Thanks
Sandip

[Sandip Kaviman]

It Seems like ranchers are on Ester vacation
[ March 20, 2008: Message edited by: Sandip Kaviman ]

[Sri Karr]

Math.round is a method which accepts one argument of two different types(double/float).There is no empty parameter method defined for Math.round, Since this method is defined to round up some number, which need to be passed to it.
1) static long round(double a)
Returns the closest long to the argument.
2) static int round(float a)
Returns the closest int to the argument.

In the example, when you are using Math.round(value[x]+0.5) inside the for loop, while iterating through the values array you are just passing values[0] which is -2.3, value[1] which is -1.0 ..values[3] to the Math.round funtion. ( Math.round( -2.3+0.5), Math(-1.0+0.5).....etc

Please try the following to understand the output.

for(int x=0;x<values.length;x++){
long j=Math.round(values[x]+.5);
double k=Math.ceil(values[x]);
System.out.println("j :"+j);
System.out.println("k :"+k);
if(Math.round(values[x]+.5) ==(Math.ceil(values[x]))){
++cnt;
}
}
System.out.println("Same results "+cnt+" times(s)");

output:
j :-2
k :-2.0
j :0
k :-1.0
j :1
k :1.0
j :5
k :4.0
Same results 2 times(s)
( cnt value is updated when j and k values are same, in this case j=-2 and k=-2.0 is same and j=1 and j=1.0 is same)

[Sandip Kaviman]

Thanks Sri,
I just missed to notice signature of round().