Here you can find the source of median(final List
| Parameter | Description |
|---|---|
| array | a list of integers |
public static <T extends Comparable<? super T>> T median(final List<T> array)
//package com.java2s; /*/*from w ww . j a va 2 s .c o m*/ * Copyright 2012-2016 Broad Institute, Inc. * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation * files (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, * 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 * conditions: * * 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. */ import java.util.*; public class Main { /** * Compute the median element of the list of integers * @param array a list of integers * @return the median element */ public static <T extends Comparable<? super T>> T median(final List<T> array) { /* TODO -- from Valentin the current implementation is not the usual median when the input is of even length. More concretely it returns the ith element of the list where i = floor(input.size() / 2). But actually that is not the "usual" definition of a median, as it is supposed to return the average of the two middle values when the sample length is an even number (i.e. median(1,2,3,4,5,6) == 3.5). [Sources: R and wikipedia] My suggestion for a solution is then: unify median and medianDoubles to public static <T extends Number> T median(Collection<T>) check on null elements and throw an exception if there are any or perhaps return a null; documented in the javadoc. relocate, rename and refactor MathUtils.median(X) to Utils.ithElement(X,X.size()/2) In addition, the current median implementation sorts the whole input list witch is O(n log n). However find out the ith element (thus calculate the median) can be done in O(n) */ if (array == null) throw new IllegalArgumentException("Array must be non-null"); final int size = array.size(); if (size == 0) throw new IllegalArgumentException("Array cannot have size 0"); else if (size == 1) return array.get(0); else { final ArrayList<T> sorted = new ArrayList<>(array); Collections.sort(sorted); return sorted.get(size / 2); } } }