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

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 ?

Answer

Use regex for a one line solution:

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

See live demo.