floats are usually good up to 6 significant digits. Your number is 676543.21 which has 8 significant digits. You will see errors past 6 digits, and those errors will easily propagate to more significant digits the more calculations you perform. If you value your sanity (or precision), use doubles. Floats can't even count past 10 million accurately.
Now, you have 2 significant digits, which suggests to me that there is a chance you want to represent currency - DO NOT . Use your own class that internally represents values using fixed-point arithmetic.
Now, as to Float.MAX_VAL which is 3.4028235E38, meaning 3.4028235*10^38 which is about 10^32 times larger than your value. Notice the 'E' in there? That's the exponent.
floats are usually good up to 6 significant digits. Your number is 676543.21 which has 8 significant digits. You will see errors past 6 digits, and those errors will easily propagate to more significant digits the more calculations you perform. If you value your sanity (or precision), use doubles. Floats can't even count past 10 million accurately.
Now, you have 2 significant digits, which suggests to me that there is a chance you want to represent currency - DO NOT . Use your own class that internally represents values using fixed-point arithmetic.
Now, as to Float.MAX_VAL which is 3.4028235E38, meaning 3.4028235*10^38 which is about 10^32 times larger than your value. Notice the 'E' in there? That's the exponent.
I love these. But I'll make it quick and painless.
Floats and decimals (aka floating points) aren't kept in the memory precisely either. But I don't want to get into float accuracy vs precision issues here, i'll just point you to a link - http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm
As far as your other question, lemme put it this way, since floats are stored in scientific notation.
floatVal = 6.765432E6 = 6.7 * 10^6
MAX_VALUE = 3.4E38 = 3.4 * 10^38
MAX_VALUE is 32 orders of magnitude bigger than your float number. Feel free to take a look at here as well http://steve.hollasch.net/cgindex/coding/ieeefloat.html
I've spent a great deal of time comparing and fixing some FP issues a few months ago...
Try to use a small delta when comparing floats. Maybe this link will help you http://introcs.cs.princeton.edu/java/91float/
floating point - How can I handle precision error with float in Java? - Stack Overflow
floating point - Retain precision with double in Java - Stack Overflow
When should I use double and when should I use float for Java?
java - Format Float to n decimal places - Stack Overflow
If you really care about precision, you should use BigDecimal
https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/math/BigDecimal.html
The problem is not with Java but with the good standard float's (http://en.wikipedia.org/wiki/IEEE_floating-point_standard).
You can either:
use Double and have a bit more precision (but not perfect of course, it also has limited precision)
use a arbitrary-precision-library
use numerically stable algorithms and truncate/round digits of which you are not sure they are correct (you can calculate numeric precision of operations)
As others have mentioned, you'll probably want to use the BigDecimal class, if you want to have an exact representation of 11.4.
Now, a little explanation into why this is happening:
The float and double primitive types in Java are floating point numbers, where the number is stored as a binary representation of a fraction and a exponent.
More specifically, a double-precision floating point value such as the double type is a 64-bit value, where:
- 1 bit denotes the sign (positive or negative).
- 11 bits for the exponent.
- 52 bits for the significant digits (the fractional part as a binary).
These parts are combined to produce a double representation of a value.
(Source: Wikipedia: Double precision)
For a detailed description of how floating point values are handled in Java, see the Section 4.2.3: Floating-Point Types, Formats, and Values of the Java Language Specification.
The byte, char, int, long types are fixed-point numbers, which are exact representions of numbers. Unlike fixed point numbers, floating point numbers will some times (safe to assume "most of the time") not be able to return an exact representation of a number. This is the reason why you end up with 11.399999999999 as the result of 5.6 + 5.8.
When requiring a value that is exact, such as 1.5 or 150.1005, you'll want to use one of the fixed-point types, which will be able to represent the number exactly.
As has been mentioned several times already, Java has a BigDecimal class which will handle very large numbers and very small numbers.
From the Java API Reference for the BigDecimal class:
Immutable, arbitrary-precision signed decimal numbers. A BigDecimal consists of an arbitrary precision integer unscaled value and a 32-bit integer scale. If zero or positive, the scale is the number of digits to the right of the decimal point. If negative, the unscaled value of the number is multiplied by ten to the power of the negation of the scale. The value of the number represented by the BigDecimal is therefore (unscaledValue × 10^-scale).
There has been many questions on Stack Overflow relating to the matter of floating point numbers and its precision. Here is a list of related questions that may be of interest:
- Why do I see a double variable initialized to some value like 21.4 as 21.399999618530273?
- How to print really big numbers in C++
- How is floating point stored? When does it matter?
- Use float or decimal for accounting application dollar amount?
If you really want to get down to the nitty gritty details of floating point numbers, take a look at What Every Computer Scientist Should Know About Floating-Point Arithmetic.
When you input a double number, for example, 33.33333333333333, the value you get is actually the closest representable double-precision value, which is exactly:
33.3333333333333285963817615993320941925048828125
Dividing that by 100 gives:
0.333333333333333285963817615993320941925048828125
which also isn't representable as a double-precision number, so again it is rounded to the nearest representable value, which is exactly:
0.3333333333333332593184650249895639717578887939453125
When you print this value out, it gets rounded yet again to 17 decimal digits, giving:
0.33333333333333326
I am learning Java, and am confuse on when to choose double or float for my real numbers or int. It feels like, it doesn’t matter because from my limited experience (with Java) both of them deliver the same results, but I don’t want to go further down the learning curve with Java and have a bad habit of using either messing up my code, and not having a clue as to why. So, when should you use float and double?