Why Does the Division of Two Integers Return 0.0 in Java

Why do I get 0.0 when I divide these two integers?

You are performing integer division, and then casting it to a double. You should be doing:

int numOfSecondsSinceMidnight = 61960;
int totalDay = 86400;
double percentDayPassed = 0;
percentDayPassed = (((double)numOfSecondsSinceMidnight / totalDay)*100);
System.out.println(percentDayPassed);

Or better yet, changing numOfSecondsSinceMidnight and totalDay to doubles:

double numOfSecondsSinceMidnight = 61960;
double totalDay = 86400;
double percentDayPassed = 0;
percentDayPassed = ((numOfSecondsSinceMidnight / totalDay)*100);
System.out.println(percentDayPassed);

Both of which print:

71.71296296296296

Why does dividing a float by an integer return 0.0?

It's because you're doing integer division.

Divide by a double or a float, and it will work:

double scale = ( n / 1024.0 ) * 255 ;

Or, if you want it as a float,

float scale = ( n / 1024.0f ) * 255 ;

Division in Java always results in zero (0)?

You're doing integer division.

You need to cast one operand to double.

Why does java return a 0?

Because you're building an integer. When you store it in a double variable, it's already too late : it's 0.

Do

double pay_per_minute = (10.0/60);

If you have variables, cast them :

double pay_per_minute = ((double)pay_per_hour) / 60;

Int division: Why is the result of 1/3 == 0?

The two operands (1 and 3) are integers, therefore integer arithmetic (division here) is used. Declaring the result variable as double just causes an implicit conversion to occur after division.

Integer division of course returns the true result of division rounded towards zero. The result of 0.333... is thus rounded down to 0 here. (Note that the processor doesn't actually do any rounding, but you can think of it that way still.)

Also, note that if both operands (numbers) are given as floats; 3.0 and 1.0, or even just the first, then floating-point arithmetic is used, giving you 0.333....

Why does double z = 1/3 result in 0.0?

The first one is an integer division really. It divides an integer by another integer (the result of which is again an integer) and assigns the result to a double variable.

Only the second one yields a double as result.

integer / integer => result is integer, even though assigned to a double variable
integer or double / double => result is double

Java: Why is this double variable coming out 0?

Make that:

double check = 3.0 / 4;

and it'll work. You got 0 because 3 / 4 is an integer division, whose value is 0.

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