Question

I’m using a float constant and setting a objects private float variable to the float constant below, but when the object outputs the value it was set to, it’s rounding up the last digit in the float.

private final float RF_FREQUENCY = 956.35625f;
Object o = new Object();
o.setRFFrequency(RF_FREQUENCY);
System.out.println(o.getRFFrequency);

Output: 956.35626

The variable in the object is declared as protected float rfFrequency; and below are the getters and setters.

public float getRFFrequency() {
        return rfFrequency;
    }
public void setRFFrequency(float value) {
        this.rfFrequency = value;
    }

Any idea why this is happening?

Answer 1

Because single precision IEEE754 floating point numbers only have 23 bits of precision (24 including the implicit 1 bit at the start).

That equates to roughly seven decimal digits and you can see that your number has eight digits in it.

All that’s happening is that the computer is choosing the closest number to what you asked for that it can represent.

If you need more precision, use a double. That gives you 52/53 bits which equates to about 15 decimal digits.