Compute the maximum (double) value of applying the given function to the given values using Lambda. - Java Lambda Stream

Java examples for Lambda Stream:DoubleFunction

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Description

Compute the maximum (double) value of applying the given function to the given values using Lambda.

Demo Code

/*/*w  ww.  j a  v  a 2  s .c o  m*/
 * www.javagl.de - Viewer - Functions
 *
 * Copyright (c) 2013-2015 Marco Hutter - http://www.javagl.de
 * 
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
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 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
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 * 
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */
//package com.java2s;

import java.util.function.DoubleFunction;

public class Main {
    /**
     * Compute the maximum (double) value of applying the given function to 
     * the given values.<br> 
     * <br>
     * If the function returns <code>null</code> or NaN for any value, this 
     * will be ignored. If the function returns <code>null</code> for all 
     * values, then <code>null</code> will be returned. If the function 
     * returns NaN for all values, then NaN will be returned.
     *  
     * @param function The function
     * @param values The values
     * @return The maximum
     */
    private static Number computeMax(
            DoubleFunction<? extends Number> function,
            Iterable<Double> values) {
        Number max = null;
        for (double x : values) {
            Number y = function.apply(x);
            max = max(max, y);
        }
        return max;
    }

    /**
     * Returns the maximum (double) of the given values.<br> 
     * <br>
     * If either value is <code>null</code>, then the other value will be 
     * returned. If both values are <code>null</code>, then <code>null</code>
     * will be returned. If neither value is <code>null</code>, and either 
     * value is NaN, then the other value will be returned. If both values 
     * are NaN, then NaN will be returned.
     * 
     * @param n0 The first value
     * @param n1 The second value 
     * @return The maximum
     */
    static Number max(Number n0, Number n1) {
        if (n0 == null) {
            return n1;
        }
        if (n1 == null) {
            return n0;
        }
        double d0 = n0.doubleValue();
        double d1 = n1.doubleValue();
        if (Double.isNaN(d0)) {
            return d1;
        }
        if (Double.isNaN(d1)) {
            return d0;
        }
        return Math.max(d0, d1);
    }
}

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