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POJava: what the return does here?
 

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    <p>I founded this code on the <a href="http://www.algorithmbase.com/258/java-priority-queue-example/" rel="nofollow">web</a> . Excuse-me if a ask here,but I haven't only understand one thing. What does exactly <strong><em>return population2 - population1;</em></strong>? It sorts the items by comparing every time each other (<strong>o1</strong> and <strong>o2</strong>) , by taking the part after the colon without any eventual spaces (leadings and finals) , so the numbers, and sorting them by...?</p> <pre><code>import java.util.Comparator; import java.util.PriorityQueue; public class Main { public static void main(String[] args) { PriorityQueue&lt;String&gt; queue = new PriorityQueue&lt;String&gt;(11, new Comparator&lt;String&gt;() { public int compare(String o1, String o2) { int population1 = Integer.parseInt(o1.split(":")[1].trim()); int population2 = Integer.parseInt(o2.split(":")[1].trim()); return population2 - population1; } }); queue.add("United States: 307006550"); queue.add("Brazil: 193733800"); queue.offer("Russia: 141850000"); queue.offer("India: 1155347700"); queue.offer("China: 1331460000"); System.out.println("Countries in database: " + queue.size()); while (!queue.isEmpty()) { System.out.println(queue.poll()); } System.out.println("Countries in database: " + queue.size()); } } </code></pre> <p>If i try to change, for example the code to:</p> <pre><code>return population1 - population2; </code></pre> <p>it orders the numbers as:</p> <pre><code>United States: 307006550 Russia: 141850000 Brazil: 193733800 India: 1155347700 China: 1331460000 </code></pre> <p>Why?</p>
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    1. COkurtzbot: excuse-me, now i've modified my last questions.
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    2. COFor all: i know that compare(arg1,arg2) or arg1.compareTo(arg2) returns a negative number if arg1<arg2,positive if arg1>arg2, else returns 0. But i would to say what's the algorithm that there's behind all this. That is,after that i inserted the first it does nothing. But from the second onwards, what exact operations it does? I hope my question is clear.
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    3. COI updated my answer after seeing the latest comment.
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