Trim from String after decimal places to 18 places in java - roundoff not required)

user_11230693 0
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I am working on a legacy code where i have String field which hold some amount value, which should have only 18 char after decimal place, not more than that.

I have achieved this like below -

        String str = "0.0040000000000000001";
    String[] values = StringUtils.split(str,".");
    System.out.println(str);
    String output = values[1];
    if(output.length()>18){
        output = output.substring(0,18);
    }
    System.out.println(values[0]+"."+output); // 0.004000000000000000

Is there any better way to do this ?

substring java
3 Answers

Use regex for a one line solution:

str = str.replaceAll("(?<=\\..{18}).*", "");

See live demo.

user_2561960

You could use a regex replacement here:

String str = "0.0040000000000000001";
String output = str.replaceAll("(\\d+\\.\\d{18})(\\d+)", "$1");
System.out.println(output); // 0.004000000000000000
user_18632290

Put it in a method, and test several alternatives to see which is better. You will have to first define what "better" means for your specific use-case: less memory? faster?

I propose:

public static String trimDecimalPlaces(String input, int places) {
    int dotPosition = input.indexOf(".");
    int targetSize = dotPosition + places + 1;
    if (dotPosition == -1 || targetSize > input.length()) {
        return input;
    } else {
        return input.substring(0, targetSize);
    }
}

This has a speed advantage over regex-based solutions, but it is certainly longer in terms of code.

user_154720
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