Long Division in Java not working as expected

Question

class LongDiv{
public static void main(String [] args){

    final long x = 24*60*60*1000*1000;
    final long y = 24*60*60*1000;
    System.out.println(x/y);
}
}

although the expected answer is 1000, but the javac gives it as 5. Reason?

Answer 1

The long x you are creating isn't the value you expected. It is in the integer range. To create longs, use:

final long x = 24L*60L*60L*1000L*1000L;
final long y = 24L*60L*60L*1000L;
System.out.println(x/y);

The x you computed, in the integer range, was 500654080. This divided by the y ( = 86400000), results in 5.794607407407407.... Java truncates the decimal part which causes the 5.

By adding an L after the number literal, you tell the compiler to compile it as a long instead of an int. The value for x you expected is 86400000000. But is was compiled as an int.

We can reproduce the wrong value for x (500654080) by truncating it to an int:

// First correct
long x = 24L*60L*60L*1000L*1000L;
/* x = `86400000000`; */
// Now truncate
x &= 0xFFFFFFFFL; // again: don't forget the L suffix
/* x = `500654080` */

Answer 2

The expressions 24*60*60*1000*1000 is an int type not a long What you want is 24L*60*60*1000*1000 which is long

This is what you have.

final long x = (24*60*60*1000*1000) & 0xFFFFFFFF;
final long y = (24*60*60*1000) & 0xFFFFFFFF;
System.out.println(x/y);

what you want is

final long x = 24L*60*60*1000*1000;
final long y = 24L*60*60*1000;
System.out.println(x/y);