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POfilling an bidimensionnal array in java
 

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  1. POfilling an bidimensionnal array in java
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    <p>I'm having some issues filling a bidimensionnal double-array out of a multi-dimensional object-array. My problem is that null value are causing a <code>java.lang.NullPointerException at IOControl.ReadCSV$1.compare(ReadCSV.java:328) at IOControl.ReadCSV$1.compare(ReadCSV.java:1) at java.util.TimSort.countRunAndMakeAscending(Unknown Source) at java.util.TimSort.sort(Unknown Source) at java.util.TimSort.sort(Unknown Source) at java.util.Arrays.sort(Unknown Source) at IOControl.ReadCSV.run(ReadCSV.java:324) at en.window.Main.main(Main.java:46)</code> , and i really don't understand why.</p> <p><strong>What am i doing ?</strong> I'm reading a CSV - file, i'm storing the input line by line, in my array of object <code>Data</code> called <code>content</code>. Then i'm filling a <code>double</code> bidimensional array called <code>sortedOutput</code> in which i would like to store <code>LeftSpeed</code> and <code>NormAvgPowOutput</code> which are double value stored in my <code>Data</code> array.</p> <p><strong>What i want :</strong> To have my <code>sortedOutput</code> bidimensionnal array sorted from the smallest to the biggest value on dimension 0 : for variable <code>LeftSpeed</code>.</p> <p>So how can i avoid the null values? Because when i try to spot them while filling my second array, the compilator says i can't compare a double to a <code>null</code> value.</p> <p>Sorry for the long post, hope you guys can help me out :) Here my code : </p> <pre><code>public void run(String path, int length) { /* * Main function of ReadCSV class. * Open / reads / closes the file. * Fills the object. */ BufferedReader br = null; String input = ""; String cvsSplitBy = ","; int[] pos = new int[200]; Data[] content = new Data[length]; Double[][] sortedOutput = new Double[length][4]; int i = 0; int j = 0; int k = 0; try { br = new BufferedReader(new FileReader(path)); while ((input = br.readLine()) != null) { // use comma as separator String[] lines = input.split(cvsSplitBy); content[i] = new Data(); if (i == 0) { //not relevant here } else { j = 0; content[i].setTime("TIME", getTime(pos[j++], lines)); content[i].setData("DATA", getContent(pos[j++], lines)); //etc } // gets rid of non coherent or useless values, e.g negative power, ... if (content[i].lhWdStdev &gt; 0 &amp;&amp; content[i].rhWdStdev &gt; 0) { normalizeData(content[i]); // not relevant content[k].setLeftSpeed(); sortedOutput[k][0] = content[k].getLeftSpeed(); sortedOutput[k][2] = content[k].getNormAvgPowOutput(); Arrays.sort(sortedOutput, new java.util.Comparator&lt;Double[]&gt;() { public int compare(Double[]a, Double[]b) { return Double.compare(a[0], b[0]); } }); } if (sortedOutput[k][0] == null) { System.out.println("FAIL"); } System.out.println("Output = " +sortedOutput[k][0]); i++; k++; } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { // Again it's not relevant } </code></pre> <p>EDIT : So finally i made 2 huge misstakes. First i tried to sort the array in the loop, that means BEFORE it was fully filled (thanks @Ted Hopp). Secondly i didn't handle the <code>null</code> values correctly. I should have checked if (<code>a != null</code>, <code>b != null</code>, <code>a[0] != null</code>, <code>b[0] != null</code> ) and then return the new order. (thanks @jboi ).</p>
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    1. COWhich line is throwing the NPE?
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    3. COIs there a reason why you implement it yourself? There are good open source libraries to do CSV parsing. Like http://opencsv.sourceforge.net/
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