Math.round() not working

Question

I'm working on a calculator in Java but the "." buttons function won't work. if I remove the Math.round() I sometimes get 1.1999999 instead of 1.2. How do I solve this problem? I've tried looking up several Math.round() solutions on stack overflow but none of them worked.

x = Math.round(x + (y / (Math.pow(10, z)) * 1000) / (double) 1000);

the code above is what I've tried so far.

At rounding issues you can also take a look into this question: [How to resolve a Java Rounding Double issue](http://stackoverflow.com/questions/179427/how-to-resolve-a-java-rounding-double-issue) — asdf, Nov 02 '16 at 15:14
How are you displaying your double? eg. 1.2 might be represented as something closer to 1.1999999. — matt, Nov 02 '16 at 15:14

score 2 · Accepted Answer · answered Nov 02 '16 at 15:09

2

You have to round the solution before dividing.

double d = x + y / Math.pow(10, z);
double r = Math.round(d * 1e3) / 1e3; // round to 3 decimal places

answered Nov 02 '16 at 15:09

Peter Lawrey

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score 0 · Answer 2 · answered Nov 02 '16 at 15:56

you can try format your text using NumberFormat class

public String formatNumber(int n){
    NumberFormat f= NumberFormat.getInstance();
    f.setMinimumFractionDigits(2);// minimum digits after comma
    f.setMaximumFractionDigits(2);//maximum digits after comma
    String formattedN = f.format(n);
    return formattedN;
}

Math.round() not working

2 Answers2