Float sum in java

Question

This is a simple add operation between two float:

float a = 3.9F;
float b = 2.95F;
Log.i("Operation","sum: "+String.valueOf(a+b));

This return me the following output:

11-26 15:02:15.680: I/Operation(18403): sum: 6.8500004

How can I obtain the correct value(6.85) ?

Take a look at http://stackoverflow.com/questions/1661273/floating-point-arithmetic-not-producing-exact-results-in-java. — tjg184, Nov 26 '13 at 14:07
Also take a look at [DecimalFormat](http://docs.oracle.com/javase/7/docs/api/java/text/DecimalFormat.html) provided in `java` api. — Andrew Schuster, Nov 26 '13 at 14:08
There's always an estimation while using Float, same thing with Double. You shall approximate to a number of decimal. Try BigDecimal instead if you need result, DecimalFormat like andrew Schuster says if you only need printing — Baptiste Gousset, Nov 26 '13 at 14:09

score 3 · Accepted Answer · answered Nov 26 '13 at 14:08

3

You should use the DecimalFormat class.

Example

DecimalFormat decFormat = new DecimalFormat("#.##");
Log.i("Operation", "sum: " + decFormat.format(a + b));

If you want to ensure that there are always going to be two decimal places, i.e: 2.90 or 2.00, then you can do something like:

DecimalFormat decFormat = new DecimalFormat("0.00");
Log.i("Operation", "sum: " + decFormat.format(a + b));

answered Nov 26 '13 at 14:08

christopher

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The number 12.90 is also correctly represented? – GVillani82 Nov 26 '13 at 14:15
It's a simple fix: `##.##` would represent `12.9`. If you insist on the `.90`, then you could have `##.00`. – christopher Nov 26 '13 at 14:16

score 0 · Answer 2 · edited Nov 26 '13 at 14:31

0

try this...

DecimalFormat format = new DecimalFormat("###.##");
String val = format.format(1.2223F+1.4334F);
System.out.println(val);

edited Nov 26 '13 at 14:31

Nunser

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answered Nov 26 '13 at 14:10

subash

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score 0 · Answer 3 · answered Nov 26 '13 at 14:14

You can use format method of System.out, so that you can decide the specific output format:

float a = 3.9F;
float b = 2.95F;
System.out.format("%.2f", a + b);

Output will be:

6.85

In here, as you can guess, %f takes float type of argument and .2 between % and f characters means you want output of this float argument with 2 decimal numbers.

Float sum in java

3 Answers3