Is there an equivalent for toPrecision() in Java?
<p>In porting an algorithm from JavaScript to Java, I've run into the problem that I need a replacement for JavaScript's toPrecision(). The problem is that I don't have a clue how small or large the numbers will be, so I can't use a simple NumberFormat with the right format.</p>

<p>Is there a standard class that offers a similar functionality?</p>

<p>EDIT
Here is what I came up with:</p>

<pre><code>   double toPrecision(double n, double p) {
        if (n==0) return 0;

        double e = Math.floor(Math.log10(Math.abs(n)));
        double f = Math.exp((e-p+1)*Math.log(10));

        return Math.round(n/f)*f;
    }
</code></pre>

<p>In principle, it does the right thing, but rounding errors completely ruin it. For example,
<code>toPrecision(12.34567, 3)</code> returns <code>12.299999999999997</code></p>

<p>EDIT 2
This version works perfectly for 11 out of 12 test cases...</p>

<pre><code>   double toPrecision(double n, double p) {
        if (n==0) return 0;

        double e = Math.floor(Math.log10(Math.abs(n)));
        double f = Math.round(Math.exp((Math.abs(e-p+1))*Math.log(10)));
        if (e-p+1&lt;0) {
            f = 1/f;
        }

        return Math.round(n/f)*f;
    }
</code></pre>

<p>But <code>toPrecision(0.00001234567, 3)</code> still returns <code>1.2299999999999999E-5</code> instead of <code>1.23E-5</code></p>
