Why Does Integer Division in Java Produce 0.0 Instead of a Decimal Result?

Why Does Java's Integer Division Result in 0.0?

When dividing two integers in Java, the result is often not what you might expect:

int totalOptCount = 500;
int totalRespCount = 1500;
float percentage = (float) (totalOptCount / totalRespCount);

In this case, you would expect percentage to be 0.33 (or 0.333 rounded). However, you may be surprised to find that it actually returns 0.0. Why is this the case?

Conversion Order to the Rescue

The reason for this unexpected result lies in the order in which Java performs its calculations. When you divide two integers, Java automatically converts them to doubles. But this conversion doesn't happen until after the division is performed. So in the above example, the calculation is actually done like this:

double percentage = totalOptCount / totalRespCount;

Which results in a double value of 0.0. To fix this issue, you need to explicitly convert one of the operands to a float or double before performing the division:

float percentage = ((float) totalOptCount) / totalRespCount;

Now, the conversion to float happens first, and the division is done on the float values, resulting in the correct float value of 0.333333.

Formatting for Decimal Precision

Once you have the correct result, you may want to format it to a specific decimal precision. You can use the String.format() method to do this:

String str = String.format("%2.02f", percentage);

This will format the percentage variable to a string with two decimal places, resulting in the value 00.33.

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