java convert from double/bigDecimal/float to string with 4decimals approximation

Question

I need precision math of maximum 4 decimals that need to be converted to string in order to proceed further with the result in my code and in case the result has more that 4decimals I would like to get the result approximation. Ex: for 3.3333333333 -> 3.3334

My current code is quite messy, but works. Is there is an easier way around this?

...............
Double rez = (Double) engine.eval(foo); // some rezult as double from the rest of code
        //convert foo to my string

 String implem = String.valueOf(rez);
 rezultat = implem;                     // rezultat -> is the string returned of the function

 if(implem.contains(".")){

 String []splitter =implem.split("\\.");
                                        //   System.out.println(splitter[0]+" length:"+splitter[0].length());
                                        //   System.out.println(splitter[1]+" length:"+splitter[1].length());
 if(splitter[1].length()>4){
 String ceva=splitter[1].substring(0,4);

     byte subb[]=ceva.getBytes();
     char c = (char)subb[3];
                                        //    System.out.println((char)subb[0]+">"+(char)subb[1]+">"+(char)subb[2]+">"+(char)subb[3]+" :those are the splits");
if(subb[0]==subb[1] && subb[1]==subb[2] && subb[2]==subb[3] && (char) subb[0]=='9'){    
//in case of 9999

long numer = Long.parseLong(splitter[0]);
numer++;
splitter[0]=String.valueOf(numer);
rezultat = splitter[0];
return rezultat;                        // program returns next Long value (without decimals)

}

                                        //   System.out.println(subb[0]+"+"+subb[1]+"+"+subb[2]+"+"+subb[3]+" value of subb[3]:"+c);
    if(c!='0'){
        int kappa = Integer.parseInt(ceva);
        kappa++;

        String partCeva = String.valueOf(kappa);                            //in case of integer<1000 -- add 0's
        while(partCeva.length()<4){
        partCeva= "0"+partCeva;
        }
           ceva=partCeva;
    }
    Double fin = Double.parseDouble(splitter[0]+"."+ceva);                  //do this to remove unwanted 0
     rezultat = fin.toString();

 }
 else{
    rezultat = splitter[0]+"."+splitter[1];
 }
...........
return rezultat ; }

Why don't use BigDecimal if you need more precision control? — Phani, Dec 03 '15 at 18:46

score 1 · Accepted Answer · answered Dec 03 '15 at 18:47

1

You can do

double x = (Double) engine.eval(foo);

To round to a String using double or float.

return String.format("%4f", x);

To round to a String using BigDecimal

return BigDecimal.valueOf(x).setScale(4, RoundingMode.HALF_UP).toString();

The value 3.3333333333 is usually rounded to 3.3333 however there is a mode which rounds up to the next value.

answered Dec 03 '15 at 18:47

Peter Lawrey

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thanks , i've gone all logical on solving this due to frustration :) will try your approach . – Sanity Dec 03 '15 at 18:57
@Sanity now you have an idea of what these libraries have to do. ;) – Peter Lawrey Dec 03 '15 at 19:00
1

String test = BigDecimal.valueOf(x).setScale(4, RoundingMode.UP).toString(); System.out.println(test); this does exactly what i need just needed to use RoundingMode.UP – Sanity Dec 03 '15 at 19:10

java convert from double/bigDecimal/float to string with 4decimals approximation

1 Answers1