In Java, I am trying to parse a string of format "###.##" to a float. The string should always have 2 decimal places.
Even if the String has value 123.00, the float should also be 123.00, not 123.0.
This is what I have so far:
System.out.println("string liters of petrol putting in preferences is " + stringLitersOfPetrol);
Float litersOfPetrol = Float.parseFloat(stringLitersOfPetrol);
DecimalFormat df = new DecimalFormat("0.00");
df.setMaximumFractionDigits(2);
litersOfPetrol = Float.parseFloat(df.format(litersOfPetrol));
System.out.println("liters of petrol before putting in editor: " + litersOfPetrol);
It prints:
string liters of petrol putting in preferences is 010.00
liters of petrol before putting in editor: 10.0
This question is related to
java
string
floating-point
number-formatting
This line is your problem:
litersOfPetrol = Float.parseFloat(df.format(litersOfPetrol));
There you formatted your float to string as you wanted, but but then that string got transformed again to a float, and then what you printed in stdout was your float that got a standard formatting. Take a look at this code
import java.text.DecimalFormat;
String stringLitersOfPetrol = "123.00";
System.out.println("string liters of petrol putting in preferences is "+stringLitersOfPetrol);
Float litersOfPetrol=Float.parseFloat(stringLitersOfPetrol);
DecimalFormat df = new DecimalFormat("0.00");
df.setMaximumFractionDigits(2);
stringLitersOfPetrol = df.format(litersOfPetrol);
System.out.println("liters of petrol before putting in editor : "+stringLitersOfPetrol);
And by the way, when you want to use decimals, forget the existence of double and float as others suggested and just use BigDecimal object, it will save you a lot of headache.
Use BigDecimal:
new BigDecimal(theInputString);
It retains all decimal digits. And you are sure of the exact representation since it uses decimal base, not binary base, to store the precision/scale/etc.
And it is not subject to precision loss like float or double are, unless you explicitly ask it to.
Float.parseFloat() is the problem as it returns a new float.
Returns a new float initialized to the value represented by the specified String, as performed by the valueOf method of class Float.
You are formatting just for the purpose of display . It doesn't mean the float will be represented by the same format internally .
You can use java.lang.BigDecimal.
I am not sure why are you using parseFloat() twice. If you want to display the float in a certain format then just format it and display it.
Float litersOfPetrol=Float.parseFloat(stringLitersOfPetrol);
DecimalFormat df = new DecimalFormat("0.00");
df.setMaximumFractionDigits(2);
System.out.println("liters of petrol before putting in editor"+df.format(litersOfPetrol));
I just want to be sure that the float number will also have 2 decimal places after converting that string.
You can't, because floating point numbers don't have decimal places. They have binary places, which aren't commensurate with decimal places.
If you want decimal places, use a decimal radix.
Java convert a String to decimal:
String dennis = "0.00000008880000";
double f = Double.parseDouble(dennis);
System.out.println(f);
System.out.println(String.format("%.7f", f));
System.out.println(String.format("%.9f", new BigDecimal(f)));
System.out.println(String.format("%.35f", new BigDecimal(f)));
System.out.println(String.format("%.2f", new BigDecimal(f)));
This prints:
8.88E-8
0.0000001
0.000000089
0.00000008880000000000000106383001366
0.00
litersOfPetrol = Float.parseFloat(df.format(litersOfPetrol));
System.out.println("liters of petrol before putting in editor : "+litersOfPetrol);
You print Float here, that has no format at all.
To print formatted float, just use
String formatted = df.format(litersOfPetrol);
System.out.println("liters of petrol before putting in editor : " + formatted);
Source: Stackoverflow.com