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  1. PO
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    <p>You can create a class named <strong>SalaryReport</strong> which is composed of many objects of <strong>SalaryReportRow</strong>.</p> <p>In a <strong>SalaryReport</strong> you have a method name <em>calculate</em>() which executes all the algorithms. <strong>SalaryReportRow</strong> can be specialized in many type of rows that suit your needs.</p> <pre><code>class SalaryReport { private List&lt;SalaryReportRow&gt; rows; private List&lt;SalaryCalculator&gt; calculators; private HashMap&lt;SalaryCalculator,List&lt;SalaryReportRow&gt;&gt; results; ... public float getResults() { } public void applyCalculators(){ for(SalaryCalculator s : calculators){ results.put(s,s.execute(rows)); } } public void setSalaryCalculators(List&lt;SalaryCalculator&gt; calculators){ this.calculators = calculators; } public float getCalculation(SalaryCalculator s){ return results.get(s); } ... } </code></pre> <p>When calculating taxes you can use a <a href="http://en.wikipedia.org/wiki/Strategy_pattern" rel="nofollow">Strategy Pattern</a> to mantain your code more flexible. If you have to combine many strategies you can use also a <a href="http://en.wikipedia.org/wiki/Composite_pattern" rel="nofollow">Composite Pattern</a> with Strategy or a <a href="http://en.wikipedia.org/wiki/Chain-of-responsibility_pattern" rel="nofollow">Chain of Responsibility</a> with Strategy.</p> <pre><code>abstract class SalaryCalculator implements Calculator { //Order of children matters protected List&lt;SalaryCalculator&gt; children = new ArrayList&lt;SalaryCalculator&gt;; public List&lt;SalaryReportRow&gt; execute(List&lt;SalaryReportRow&gt; rows){ List&lt;SalaryReportRow&gt; result_rows = new ArrayList&lt;SalaryReportRow&gt; (rows); for(SalaryCalculator s: children){ result_rows = s.execute(result_rows); } return result_rows; } } class TaxCalculator extends SalaryCalculator { public List&lt;SalaryReportRow&gt; execute(List&lt;SalaryReportRow&gt; rows){ List&lt;SalaryReportRow&gt; result_rows = super.execute(rows); // } } class MaxSalaryCalculator extends SalaryCalculator { public List&lt;SalaryReportRow&gt; execute(List&lt;SalaryReportRow&gt; rows){ List&lt;SalaryReportRow&gt; result_rows = super.execute(rows); ... } } class MaxSalaryWithTaxCalculator extends SalaryCalculator { public MaxSalaryWithTaxCalculator() { children.add(new MaxSalaryCalculator()); children.add(new TaxCalculator()); } public List&lt;SalaryReportRow&gt; execute(List&lt;SalaryReportRow&gt; rows){ List&lt;SalaryReportRow&gt; result_rows = super.execute(rows); ... } } </code></pre> <p>So the <strong>SalaryReport</strong> will have a method called <em>setSalaryCalculators(List)</em> (you can use also more than one algorithms at once), where List is a list that contains all the strategies applied.</p> <p>You will have more <strong>SalaryReportRows</strong>:</p> <ol> <li>One for taxes.</li> <li>One for money earned.</li> <li>...</li> </ol> <p>So you can easily calculate all steps.</p> <p>When you communicate with storage handlers I suggest to use a <a href="http://www.oracle.com/technetwork/java/dataaccessobject-138824.html" rel="nofollow">DAO pattern</a> with interfaces which is responsible of creating and saving objects.</p> <p>I hope this will be helpful. :)</p>
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    1. PODesign Pattern to track partial results of a complex process
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    1. USIdipaolo
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    1. COThere is something that you misunderstood, I don't need the sum of the partial values, what I need is the different partial "states" of the amount. For example: original amount: 100. Amount with tax: 110. Amount with tax restricted by a maximum: 90. Amount with tax restricted by amount an with a second tax: 95. This last value is used by the application for make another calculations, like a mean, and so on. But for the last "screen" of my application I have to show the detail of the calculations to the user. Imagine a kind of spreadsheet with the details of each "step" to get the last amount
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    2. COAlso, I've tried to use the Strategy Pattern for what you propose but I faced a problem: My different "tax applying" strategies (actually, those aren't so simple like the example ones) requires different "parameters", so, I couldn't make a common interface for the Strategy Pattern. And that is another problem that I have hehe
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    3. COI just notice I made some mistakes on the code, I just edited the original post and fixed it. Also I add a quick sample of the kind of report I need. Thanks for the help @Idipaolo
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