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    <p>Aside from the syntax issues, it seems strange to me to use an array and a linked list to represent a matrix. To be able to access arbitrary cells of the matrix, you would probably want an actual array or at least an <code>ArrayList</code> to hold the rows, as <code>LinkedList</code> must traverse the whole list from the first element to any particular element, an <code>O(n)</code> operation, as opposed to the much quicker <code>O(1)</code> with <code>ArrayList</code> or an actual array.</p> <p>Since you mentioned this matrix is sparse, though, perhaps a better way to store the data is as a map of maps, where a key in the first map represents a row index, and its value is a row map whose keys are a column index, with the value being your IntegerNode class. Thus:</p> <pre><code>private Map&lt;Integer, Map&lt;Integer, IntegerNode&gt;&gt; myMatrix = new HashMap&lt;Integer, Map&lt;Integer, IntegerNode&gt;&gt;(); // access a matrix cell: int rowIdx = 100; int colIdx = 30; Map&lt;Integer, IntegerNode&gt; row = myMatrix.get(rowIdx); // if null, create and add to matrix IntegerNode node = row.get(colIdx); // possibly null </code></pre> <p>If you need to be able to traverse the matrix row by row, you can make the row map type a <code>TreeMap</code>, and same for traversing the columns in index order, but if you don't need those cases, <code>HashMap</code> is quicker than <code>TreeMap</code>. Helper methods to get and set an arbitrary cell, handling unset null values, would be useful, of course.</p>
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