{"id":1897,"date":"2015-08-07T11:45:07","date_gmt":"2015-08-07T10:45:07","guid":{"rendered":"http:\/\/blog.davidkeen.com\/?p=1897"},"modified":"2025-10-23T10:18:52","modified_gmt":"2025-10-22T23:48:52","slug":"calculating-distance-with-a-java-8-collector","status":"publish","type":"post","link":"https:\/\/davidkeen.com\/blog\/2015\/08\/calculating-distance-with-a-java-8-collector\/","title":{"rendered":"Calculating distance with a Java 8 Collector"},"content":{"rendered":"\n<p>In <a href=\"http:\/\/blog.davidkeen.com\/2013\/10\/calculating-distance-with-scalas-foldleft\/\">a previous post<\/a> I showed a way to calculate the total distance of a GPX track using Scala&#8217;s foldLeft. Continuing my current hobby of exploring the new Java 8 lambdas and streams API I thought I would see how the functional approach translated to Java.<\/p>\n\n\n\n<p>To recap, a GPX track is just a sequence of latitude, longitude pairs. The first problem is that Java doesn&#8217;t have Scala&#8217;s handy tuples so we need a custom class to represent a point.<\/p>\n\n\n\n<div class=\"wp-block-kevinbatdorf-code-block-pro\" data-code-block-pro-font-family=\"Code-Pro-JetBrains-Mono\" style=\"font-size:.875rem;font-family:Code-Pro-JetBrains-Mono,ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,monospace;line-height:1.25rem;--cbp-tab-width:2;tab-size:var(--cbp-tab-width, 2)\"><span style=\"display:block;padding:16px 0 0 16px;margin-bottom:-1px;width:100%;text-align:left;background-color:#2e3440ff\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"54\" height=\"14\" viewBox=\"0 0 54 14\"><g fill=\"none\" fill-rule=\"evenodd\" transform=\"translate(1 1)\"><circle cx=\"6\" cy=\"6\" r=\"6\" fill=\"#FF5F56\" stroke=\"#E0443E\" stroke-width=\".5\"><\/circle><circle cx=\"26\" cy=\"6\" r=\"6\" fill=\"#FFBD2E\" stroke=\"#DEA123\" stroke-width=\".5\"><\/circle><circle cx=\"46\" cy=\"6\" r=\"6\" fill=\"#27C93F\" stroke=\"#1AAB29\" stroke-width=\".5\"><\/circle><\/g><\/svg><\/span><span role=\"button\" tabindex=\"0\" style=\"color:#d8dee9ff;display:none\" aria-label=\"Copy\" class=\"code-block-pro-copy-button\"><pre class=\"code-block-pro-copy-button-pre\" aria-hidden=\"true\"><textarea class=\"code-block-pro-copy-button-textarea\" tabindex=\"-1\" aria-hidden=\"true\" readonly>class Point {\n    public final double lat;\n    public final double lon;\n\n    public Point(double lat, double lon) {\n        this.lat = lat;\n        this.lon = lon;\n    }\n}<\/textarea><\/pre><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"width:24px;height:24px\" fill=\"none\" viewBox=\"0 0 24 24\" stroke=\"currentColor\" stroke-width=\"2\"><path class=\"with-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2m-6 9l2 2 4-4\"><\/path><path class=\"without-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2\"><\/path><\/svg><\/span><pre class=\"shiki nord\" style=\"background-color: #2e3440ff\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color: #81A1C1\">class<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">final<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">final<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">Point<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">this<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> lat<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">this<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> lon<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><span style=\"color: #ECEFF4\">}<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n<p>My first thought was to use the reduce method on the Stream interface but given the slightly more complicated requirement to keep track of both the total distance and the previous point I ended up implementing a custom <a href=\"https:\/\/docs.oracle.com\/javase\/8\/docs\/api\/java\/util\/stream\/Collector.html\">Collector<\/a>. From the Javadoc a Collector is:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>A mutable reduction operation that accumulates input elements into a mutable result container, optionally transforming the accumulated result into a final representation after all input elements have been processed. Reduction operations can be performed either sequentially or in parallel.<\/p>\n<\/blockquote>\n\n\n\n<p>The Collector interface has three type parameters: T is the type of input elements to the reduction operation, A is the mutable accumulation type of the reduction operation and R is the result type of the reduction operation.<\/p>\n\n\n\n<p>In our case, the input elements are Points and the result type is a Double (distance in miles). We just need a mutable accumulation type to keep track of the total distance and the last point in the track. Here it is:<\/p>\n\n\n\n<div class=\"wp-block-kevinbatdorf-code-block-pro\" data-code-block-pro-font-family=\"Code-Pro-JetBrains-Mono\" style=\"font-size:.875rem;font-family:Code-Pro-JetBrains-Mono,ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,monospace;line-height:1.25rem;--cbp-tab-width:2;tab-size:var(--cbp-tab-width, 2)\"><span style=\"display:block;padding:16px 0 0 16px;margin-bottom:-1px;width:100%;text-align:left;background-color:#2e3440ff\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"54\" height=\"14\" viewBox=\"0 0 54 14\"><g fill=\"none\" fill-rule=\"evenodd\" transform=\"translate(1 1)\"><circle cx=\"6\" cy=\"6\" r=\"6\" fill=\"#FF5F56\" stroke=\"#E0443E\" stroke-width=\".5\"><\/circle><circle cx=\"26\" cy=\"6\" r=\"6\" fill=\"#FFBD2E\" stroke=\"#DEA123\" stroke-width=\".5\"><\/circle><circle cx=\"46\" cy=\"6\" r=\"6\" fill=\"#27C93F\" stroke=\"#1AAB29\" stroke-width=\".5\"><\/circle><\/g><\/svg><\/span><span role=\"button\" tabindex=\"0\" style=\"color:#d8dee9ff;display:none\" aria-label=\"Copy\" class=\"code-block-pro-copy-button\"><pre class=\"code-block-pro-copy-button-pre\" aria-hidden=\"true\"><textarea class=\"code-block-pro-copy-button-textarea\" tabindex=\"-1\" aria-hidden=\"true\" readonly>class Result {\n    private Point previousPoint;\n    private double totalDistance = 0.0;\n}<\/textarea><\/pre><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"width:24px;height:24px\" fill=\"none\" viewBox=\"0 0 24 24\" stroke=\"currentColor\" stroke-width=\"2\"><path class=\"with-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2m-6 9l2 2 4-4\"><\/path><path class=\"without-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2\"><\/path><\/svg><\/span><pre class=\"shiki nord\" style=\"background-color: #2e3440ff\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color: #81A1C1\">class<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">private<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">previousPoint<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">private<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">totalDistance<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">0.0<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #ECEFF4\">}<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n<p>So we have an input type and an accumulation type. Now we can implement the Collector which uses the <a href=\"https:\/\/en.wikipedia.org\/wiki\/Haversine_formula\">haversine formula<\/a> to calculate great circle distance between each point in the track and put it all together:<\/p>\n\n\n\n<div class=\"wp-block-kevinbatdorf-code-block-pro\" data-code-block-pro-font-family=\"Code-Pro-JetBrains-Mono\" style=\"font-size:.875rem;font-family:Code-Pro-JetBrains-Mono,ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,monospace;line-height:1.25rem;--cbp-tab-width:2;tab-size:var(--cbp-tab-width, 2)\"><span style=\"display:block;padding:16px 0 0 16px;margin-bottom:-1px;width:100%;text-align:left;background-color:#2e3440ff\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"54\" height=\"14\" viewBox=\"0 0 54 14\"><g fill=\"none\" fill-rule=\"evenodd\" transform=\"translate(1 1)\"><circle cx=\"6\" cy=\"6\" r=\"6\" fill=\"#FF5F56\" stroke=\"#E0443E\" stroke-width=\".5\"><\/circle><circle cx=\"26\" cy=\"6\" r=\"6\" fill=\"#FFBD2E\" stroke=\"#DEA123\" stroke-width=\".5\"><\/circle><circle cx=\"46\" cy=\"6\" r=\"6\" fill=\"#27C93F\" stroke=\"#1AAB29\" stroke-width=\".5\"><\/circle><\/g><\/svg><\/span><span role=\"button\" tabindex=\"0\" style=\"color:#d8dee9ff;display:none\" aria-label=\"Copy\" class=\"code-block-pro-copy-button\"><pre class=\"code-block-pro-copy-button-pre\" aria-hidden=\"true\"><textarea class=\"code-block-pro-copy-button-textarea\" tabindex=\"-1\" aria-hidden=\"true\" readonly>package com.davidkeen.test;\n\nimport com.google.common.collect.ImmutableList;\n\nimport java.util.Collections;\nimport java.util.List;\nimport java.util.Set;\nimport java.util.function.BiConsumer;\nimport java.util.function.BinaryOperator;\nimport java.util.function.Function;\nimport java.util.function.Supplier;\nimport java.util.stream.Collector;\n\npublic class GpxDistanceCalculator {\n\n    public static class Point {\n        public final double lat;\n        public final double lon;\n\n        public Point(double lat, double lon) {\n            this.lat = lat;\n            this.lon = lon;\n        }\n    }\n\n    private static class Result {\n        private Point previousPoint;\n        private double totalDistance = 0.0;\n    }\n    \n    public static class GpxCollector implements Collector&lt;Point, Result, Double> {\n\n        public static double haversineDistance(Point pointA, Point pointB) {\n            double deltaLat = Math.toRadians(pointB.lat - pointA.lat);\n            double deltaLong = Math.toRadians(pointB.lon - pointA.lon);\n            double a = Math.pow(Math.sin(deltaLat \/ 2), 2) + Math.cos(Math.toRadians(pointA.lat)) *\n                    Math.cos(Math.toRadians(pointB.lat)) * Math.pow(Math.sin(deltaLong \/ 2), 2);\n            double greatCircleDistance = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));\n            return 3958.761 * greatCircleDistance;\n        }\n\n        @Override\n        public Supplier&lt;Result> supplier() {\n            return Result::new;\n        }\n\n        @Override\n        public BiConsumer&lt;Result, Point> accumulator() {\n            return (accumulator, entry) -> {\n                if (accumulator.previousPoint != null) {\n                    accumulator.totalDistance += haversineDistance(accumulator.previousPoint, entry);\n                }\n                accumulator.previousPoint = entry;\n            };\n        }\n\n        @Override\n        public BinaryOperator&lt;Result> combiner() {\n\n            \/\/ Should not be processed in a parallel stream\n            return null;\n        }\n\n        @Override\n        public Function&lt;Result, Double> finisher() {\n            return accumulator -> accumulator.totalDistance;\n        }\n\n        @Override\n        public Set&lt;Characteristics> characteristics() {\n            return Collections.emptySet();\n        }\n    }\n\n    public static void main(String[] args) {\n        List&lt;Point> track = new ImmutableList.Builder&lt;Point>()\n                .add(new Point(51.168437004089355, -0.648922920227051))\n                .add(new Point(51.16805076599121, -0.64918041229248))\n                .add(new Point(51.16757869720459, -0.64995288848877))\n                .build();\n        double distance = track.stream().collect(new GpxCollector());\n        System.out.println(\"Total distance: \" + distance + \" miles\");\n    }\n}\n<\/textarea><\/pre><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"width:24px;height:24px\" fill=\"none\" viewBox=\"0 0 24 24\" stroke=\"currentColor\" stroke-width=\"2\"><path class=\"with-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2m-6 9l2 2 4-4\"><\/path><path class=\"without-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2\"><\/path><\/svg><\/span><pre class=\"shiki nord\" style=\"background-color: #2e3440ff\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color: #81A1C1\">package<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">com<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">davidkeen<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">test<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">com<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">google<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">common<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">collect<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">ImmutableList<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">Collections<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">List<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">Set<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">function<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">BiConsumer<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">function<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">BinaryOperator<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">function<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">Function<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">function<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">Supplier<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">import<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">java<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">util<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">stream<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">Collector<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">class<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">GpxDistanceCalculator<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">static<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">class<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">final<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">final<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">Point<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">this<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> lat<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">this<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> lon<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">private<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">static<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">class<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">private<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">previousPoint<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">private<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">totalDistance<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">0.0<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">static<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">class<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">GpxCollector<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">implements<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB; font-weight: bold\">Collector<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Double<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">static<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">haversineDistance<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">pointA<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">pointB<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">deltaLat<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">toRadians<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">pointB<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">-<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">pointA<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">deltaLong<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">toRadians<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">pointB<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">-<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">pointA<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lon<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">a<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">pow<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">sin<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9FF\">deltaLat <\/span><span style=\"color: #81A1C1\">\/<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">2<\/span><span style=\"color: #ECEFF4\">),<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">2<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">+<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">cos<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">toRadians<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">pointA<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #ECEFF4\">))<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">*<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                    <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">cos<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">toRadians<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">pointB<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">lat<\/span><span style=\"color: #ECEFF4\">))<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">*<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">pow<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">sin<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9FF\">deltaLong <\/span><span style=\"color: #81A1C1\">\/<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">2<\/span><span style=\"color: #ECEFF4\">),<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">2<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">greatCircleDistance<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">2<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">*<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">atan2<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">sqrt<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9FF\">a<\/span><span style=\"color: #ECEFF4\">),<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Math<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">sqrt<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #B48EAD\">1<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">-<\/span><span style=\"color: #D8DEE9FF\"> a<\/span><span style=\"color: #ECEFF4\">))<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">return<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #B48EAD\">3958.761<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">*<\/span><span style=\"color: #D8DEE9FF\"> greatCircleDistance<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">@<\/span><span style=\"color: #D08770\">Override<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Supplier<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">supplier<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">return<\/span><span style=\"color: #D8DEE9FF\"> Result<\/span><span style=\"color: #81A1C1\">::new;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">@<\/span><span style=\"color: #D08770\">Override<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">BiConsumer<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">accumulator<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">return<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9FF\">accumulator<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> entry<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">-&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #81A1C1\">if<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">accumulator<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">previousPoint<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">!=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">null<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                    <\/span><span style=\"color: #D8DEE9\">accumulator<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">totalDistance<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">+=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">haversineDistance<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #D8DEE9\">accumulator<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">previousPoint<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> entry<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #D8DEE9\">accumulator<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">previousPoint<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> entry<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #ECEFF4\">}<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">@<\/span><span style=\"color: #D08770\">Override<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">BinaryOperator<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">combiner<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #ECEFF4\">            <\/span><span style=\"color: #616E88\">\/\/ Should not be processed in a parallel stream<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">return<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">null;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">@<\/span><span style=\"color: #D08770\">Override<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Function<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Result<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Double<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">finisher<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">return<\/span><span style=\"color: #D8DEE9FF\"> accumulator <\/span><span style=\"color: #8FBCBB\">-&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">accumulator<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">totalDistance<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">@<\/span><span style=\"color: #D08770\">Override<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">Set<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Characteristics<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">characteristics<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">            <\/span><span style=\"color: #81A1C1\">return<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">Collections<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">emptySet<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #81A1C1\">public<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">static<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">void<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">main<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #8FBCBB\">String<\/span><span style=\"color: #ECEFF4\">[]<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">args<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">{<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #8FBCBB\">List<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #ECEFF4\">&gt;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">track<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">new<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #8FBCBB\">ImmutableList<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #8FBCBB\">Builder<\/span><span style=\"color: #ECEFF4\">&lt;<\/span><span style=\"color: #8FBCBB\">Point<\/span><span style=\"color: #ECEFF4\">&gt;()<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">add<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #81A1C1\">new<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">Point<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #B48EAD\">51.168437004089355<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">-<\/span><span style=\"color: #B48EAD\">0.648922920227051<\/span><span style=\"color: #ECEFF4\">))<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">add<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #81A1C1\">new<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">Point<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #B48EAD\">51.16805076599121<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">-<\/span><span style=\"color: #B48EAD\">0.64918041229248<\/span><span style=\"color: #ECEFF4\">))<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">add<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #81A1C1\">new<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">Point<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #B48EAD\">51.16757869720459<\/span><span style=\"color: #ECEFF4\">,<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">-<\/span><span style=\"color: #B48EAD\">0.64995288848877<\/span><span style=\"color: #ECEFF4\">))<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">                <\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">build<\/span><span style=\"color: #ECEFF4\">()<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #81A1C1\">double<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">distance<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">=<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #D8DEE9\">track<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">stream<\/span><span style=\"color: #ECEFF4\">().<\/span><span style=\"color: #88C0D0\">collect<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #81A1C1\">new<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #88C0D0\">GpxCollector<\/span><span style=\"color: #ECEFF4\">())<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">        <\/span><span style=\"color: #D8DEE9\">System<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #D8DEE9\">out<\/span><span style=\"color: #ECEFF4\">.<\/span><span style=\"color: #88C0D0\">println<\/span><span style=\"color: #ECEFF4\">(<\/span><span style=\"color: #ECEFF4\">&quot;<\/span><span style=\"color: #A3BE8C\">Total distance: <\/span><span style=\"color: #ECEFF4\">&quot;<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #81A1C1\">+<\/span><span style=\"color: #D8DEE9FF\"> distance <\/span><span style=\"color: #81A1C1\">+<\/span><span style=\"color: #D8DEE9FF\"> <\/span><span style=\"color: #ECEFF4\">&quot;<\/span><span style=\"color: #A3BE8C\"> miles<\/span><span style=\"color: #ECEFF4\">&quot;<\/span><span style=\"color: #ECEFF4\">)<\/span><span style=\"color: #81A1C1\">;<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">    <\/span><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><span style=\"color: #ECEFF4\">}<\/span><\/span>\n<span class=\"line\"><\/span><\/code><\/pre><\/div>\n\n\n\n<p>So given that we need to implement a Point class and a custom Collector the end result isn&#8217;t quite as concise as Scala but it&#8217;s still a nice functional way of processing the list. Unfortunately we can&#8217;t take advantage of parallel streams as the points have to be processed in order. The more I use Java 8&#8217;s new streams and lambdas the more I like them and Collectors are a nice way of customising reduction.<\/p>\n\n\n\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In a previous post I showed a way to calculate the total distance of a GPX track using Scala&#8217;s foldLeft. Continuing my current hobby of exploring the new Java 8 lambdas and streams API I thought I would see how the functional approach translated to Java. To recap, a GPX track is just a sequence [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2639,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[25],"tags":[],"class_list":["post-1897","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-dev"],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/davidkeen.com\/blog\/wp-content\/uploads\/2015\/08\/pexels-photo-416974.jpeg?fit=1280%2C960&ssl=1","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/posts\/1897","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/comments?post=1897"}],"version-history":[{"count":6,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/posts\/1897\/revisions"}],"predecessor-version":[{"id":2850,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/posts\/1897\/revisions\/2850"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/media\/2639"}],"wp:attachment":[{"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/media?parent=1897"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/categories?post=1897"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/davidkeen.com\/blog\/wp-json\/wp\/v2\/tags?post=1897"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}