Floating point precision and equality in Java

Question

It\'s know that floating point number, even those with fixed digits after decimal point in decimal format, can\'t be represented exactly. So I have the following program to test

Answer 1

1. I am suspicious of System.out.printf working correctly here. A reliable way to get the exact double value you get when you write 0.1 is to write new BigDecimal(0.1).toString().
2. "Why does 0.1f + 0.2f == 0.3f return true?" Pretty much because you just got lucky: rounding 0.1 to the closest float representation and 0.2 to the closest float representation and adding them gets you the closest representable float to 0.3. That's not true in general, those values just happen to work.