Java Double Number Round round(double value, int numDecimals)

Description

Round a value to the specified number of decimal places using the "Round Half Up" strategy.

License

Open Source License

Parameter

Parameter	Description
value	The value to round
numDecimals	The number of decimal places to round to.

Return

The value rounded to the specified number of decimals

Declaration

public static double round(double value, int numDecimals) 

Method Source Code

//package com.java2s;
/* (c) 2016 Open Source Geospatial Foundation - all rights reserved
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.//from w w  w.  j  av  a 2 s  .  c om
 */

public class Main {
    private static double[] SCALE = { 1d, 10d, 100d, 1000d, 10000d,
            100000d, 1000000d, 10000000d, 100000000d };

    /**
     * Round a value to the specified number of decimal places using the "Round Half Up" strategy.
     * 
     * <p>
     * Special cases:
     * <ul>
     * <li>NaN is returned as NaN.<li>
     * <li>+/-Infinity are returned as +/-Infinity.
     * </ul>
     * 
     * @param value The value to round
     * @param numDecimals The number of decimal places to round to.
     * 
     * @return The value rounded to the specified number of decimals
     */
    public static double round(double value, int numDecimals) {
        // Technically this code will handle -numDecimals by rounding digits to the left of the decimal point, but that is
        // probably a use case that is not really needed in practice.

        double scale = (numDecimals < 8) ? SCALE[numDecimals] : Math.pow(
                10, numDecimals);

        // Prevent us exceeding the maximum precision.  We make sure the minimum spacing between values is sufficient
        // for the given scale otherwise just return the value.
        if (Math.ulp(value) * scale > 1d)
            return value;

        return Math.floor(value * scale + 0.5) / scale;
    }
}

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2. round(double value, int decimals)
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