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POSorting a 2D Integer array based on a column
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  1. POSorting a 2D Integer array based on a column
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    copied!<p>I have a 2D-array that I want to sort based on the second column. The first column should remain paired with the second column.</p> <p>The 2D-array is initially as follows (2x10 matrix):</p> <pre><code>0 10 1 9 2 9 3 9 4 15 5 10 6 4 7 8 8 11 9 12 </code></pre> <p>I want the above 2D-array to be sorted like this:</p> <pre><code>4 15 9 12 8 11 0 10 5 10 1 9 2 9 3 9 7 8 6 4 </code></pre> <p>Now, I've tried adapting the answer from: <a href="https://stackoverflow.com/questions/4907683/sort-a-two-dimensional-array-based-on-one-column">Sort a two dimensional array based on one column</a> into this code:</p> <pre><code>Arrays.sort(theArray, new Comparator&lt;Integer[]&gt;() { @Override public int compare(Integer[] int1, Integer[] int2) { Integer numOfKeys1 = int1[1]; Integer numOfKeys2 = int2[1]; return numOfKeys1.compareTo(numOfKeys2); } }); </code></pre> <p>However, it doesn't seem to sort the array at all. When printing the array after calling the sort() function the array is in its initial order.</p> <p>I also tried adapting the answer from here: <a href="https://stackoverflow.com/questions/5064027/sorting-2d-array-of-string-in-java">sorting 2D array of String in java</a> but I encountered the same problem.</p> <p>Have I made some fatal mistake when adapting these solutions, or should my code work?</p> <p>Also, how would I go about sorting this array in descending order? Would I replace the return statement in compare() with this line?</p> <pre><code>return -numOfKeys2.compareTo(numOfKeys1); </code></pre> <p>Any help would be greatly appreciated. Thanks!</p> <p>EDIT: Just posting the rest of my code to see if the problem is elsewhere.</p> <pre><code>public void Sort() { Integer[][] theArray = {{0,10},{1,9},{2,9},{3,9},{4,15},{5,10},{6,4},{7,8},{8,11},{9,12}};; dump(theArray); Arrays.sort(theArray, new Comparator&lt;Integer[]&gt;() { @Override public int compare(Integer[] int1, Integer[] int2) { Integer numOfKeys1 = int1[1]; Integer numOfKeys2 = int2[1]; return numOfKeys1.compareTo(numOfKeys2); } }); System.out.println("===="); dump(theArray); } public void dump(Integer[][] array) { for(int p = 0, q = 10; p &lt; q; p++) { System.out.println(array[p][0] + " " + array[p][1]); } } </code></pre> <p>EDIT 2:</p> <p>I've got it working. Thanks everyone for your help. I had multiple Sort() functions (an older one that wasn't working, and the one you see above), and it turns out I was calling the wrong one, even though I thought I changed the call. Just one of those days.</p> <p>Feel free to use the code above if you want to sort an array. It's fully working now.</p>
 

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