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Ridding Myself from Trailing Digits on Dollar Amts

Posted on 1998-08-14
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Last Modified: 2010-05-18
I'm trying to get a dollar amount in the format of $xx.xx.  Using the double datatype, when I multiply two numbers, sometimes I get a format of $xx.00000000007.  I know its stupid, but how can I restrict the output to only two digits after the decimal point?
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Question by:earlmoore
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4 Comments
 

Author Comment

by:earlmoore
ID: 1232862
Edited text of question
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Expert Comment

by:awilkins
ID: 1232863
One way to do this would be to ues a long instead of a double to represent your dollar amount.  This long would then represent the total number of cents.
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Expert Comment

by:imladris
ID: 1232864
Whenever I need to deal with dollars, I avoid float and double like the plague. When you multiply and divide, you can easily get results that are ever so slightly off. I have found it far better to stick with int or long. Multiply the dollar values, add 50 and divide by 100 for a rounded result. (Add 0 to truncate, and 99 to round high).
Output can be done with something like:

StringBuffer dv=new StringBuffer(Integer.toString(dlr));
dv.insert(dv.length()-2,'.');
String dlrstr=dv.toString();

This produces the right string, and could be captured in some utility method.


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Accepted Solution

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threshold earned 300 total points
ID: 1232865
In Java, JVM stores the double/float into binary code(IEEE 754)
if you assign 1.05 into double a, there is no binary code that can represent 1.05 exactly.
The JVM just choose the nearest one, so you will got 1.0500000000004...

To calculate currency, you should :
1. use the BigDecimal to calculate/print currency explicitly.
2. use the double and DecimalFormat to print double.

String input_string=myTextField.getText(); // maybe you need to skip the '$' first.
double a=(new Double(input_string)).doubleValue();
DecimalFormat format=new DecimalFormat('###,###,###.##');
System.out.println ("Result : "+format.format(a+0.005)); // to display the neighborhood in the format

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