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copied!<p>The <code>rowKeySet()</code> is the set of all rows and the <code>columnKeySet()</code> is the set of all columns for the table. However, it may well not be the case that there is a value for every combination of row key and column key. For example, maybe you only calculated a result with a certain <code>RowValue</code> for one of the <code>Data</code> objects. The combination of that <code>RowValue</code> object (row key) and any other <code>Data</code> object (column key) would not map to a <code>Result</code> in that case. It seems likely that you're seeing something like this.</p> <p>To only iterate over the valid mappings, you'd want to do something like this:</p> <pre><code>for (RowValue row : results.rowKeySet()) { // Only iterate over the columns that actually have values for this row for (Data d : results.row(row).keySet()) { System.out.println(results.get(row, d)); } } </code></pre> <p><strong>Edit:</strong></p> <p>From my understanding of what's happening, no <code>null</code> is being set as a value in the table. Rather, something like this is happening:</p> <pre><code>Table<Integer, Integer, String> table = TreeBasedTable.create(); table.put(1, 1, "Foo"); table.put(2, 2, "Bar"); </code></pre> <p>Note that in the entire table, there are rows <code>1</code> and <code>2</code> and columns <code>1</code> and <code>2</code>. However, there is only a value at column <code>1</code> of row <code>1</code> and at column <code>2</code> of row <code>2</code>. So when we iterate through every possible combination of row and column, as you do in your example, we print out the values at row <code>1</code>, column <code>2</code> and at row <code>2</code>, column <code>1</code>, both of which return <code>null</code> since no value was placed at those cells... calling <code>table.contains(1, 2)</code> returns <code>false</code>.</p>

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