How to a parse a string into a float with three decimal points in java

Question

I know there is a way of forcing a float to have 3 decimal points, but how do I make a string representation "4.00000009" retain 3 decimal points after I turn it into a float? Float.parseFloat() rounds it to 4.0. Not using extra libraries would be ideal.

It's simply a requirement that I have to have 3 decimal points, regardless of the equivalence in values. — Rik Johnson
– Rik Johnson, Commented Mar 4, 2017 at 19:08
@DannyLiang Can you elaborate? As Joseph said, 4.0 = 4.000. A string representation of a float can have a specific format, a float doesn't. — BackSlash
– BackSlash, Commented Mar 4, 2017 at 19:09
substring would just turn it into another string with the correct rounding correct? I need a float — Rik Johnson
– Rik Johnson, Commented Mar 4, 2017 at 19:09

corsiKa · Accepted Answer · 2017-03-04 19:09:42Z

1

If you're guaranteed that the String is properly formatted, you can take a substring based on the index of the decimal.

Alternatively, you can parse it, multiply by a thousand, round it, and divide it by a thousand.

However, this is going to be bad for you in the long run. Floating point numbers don't fare so well when exact values are needed. Consider BigDecimal instead.

answered Mar 4, 2017 at 19:09

corsiKa

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Gooz · Accepted Answer · 2017-03-04 19:20:57Z

1

This utility method takes a String and turns it into a float with 3 decimals places:

public static float getFloat(String s) {
    BigDecimal decimal = new BigDecimal(s);
    decimal = decimal.setScale(3, RoundingMode.HALF_UP);
    return decimal.floatValue();
}

edited Mar 4, 2017 at 19:20

answered Mar 4, 2017 at 19:17

Gooz

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LppEdd Over a year ago

BigDecimal is the answer

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