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POcode reuse in Methods.class vs strategy pattern and dependency injection
 

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    <p><strong><code>Status:</code></strong> Answers of Fendy and Glen Best are <strong>equally acceptable</strong> and honored by me but since one can be accepted and bounty be given, I choose Fendy's answer.</p> <p><strong><code>Scenario:</code></strong></p> <p>If I have <strong>some code</strong> that has <strong>to be reused many times</strong> in <strong>many classes</strong> (rarely with minor parameter changes which is obvious) and concurrent threads, Which approach to go for?</p> <p>The code that has to be reused can be any sane thing (with appropriate care of static and non-static context in mind and method making techniques). It can be an algorithm, A DB method doing connect,operate,close. Anything.</p> <ol> <li><p>Make some class like <code>MyMethods.class</code> and <strong>put all those methods in it</strong>. </p> <p>1.a. Make <strong>methods</strong> <code>static</code> and call (by all classes and concurrent threads) directly as <code>MyMethods.someMethod();</code></p> <p>1.b. Make <strong>methods</strong> <code>non-static</code> and at the time to call them, <strong><code>instantiate</code> the whole class</strong> by <code>MyMethods mm = MyMethods(); mm.someMethod();</code></p></li> <li><p>Use <strong>Strategy pattern</strong> stated at <a href="https://en.wikipedia.org/wiki/Strategy_pattern" rel="nofollow">https://en.wikipedia.org/wiki/Strategy_pattern</a> (code attached here with).</p></li> <li><p>Use <strong>dependency injection</strong> stated at <a href="https://en.wikipedia.org/wiki/Dependency_injection#Java" rel="nofollow">https://en.wikipedia.org/wiki/Dependency_injection#Java</a></p></li> </ol> <p><strong><code>Problems:</code></strong></p> <ol> <li><p>Some people would say <strong>Unit test</strong> <a href="http://en.wikipedia.org/wiki/Unit_testing" rel="nofollow">http://en.wikipedia.org/wiki/Unit_testing</a> <strong>wont be possible</strong> with this approach, will make <strong>trouble in swaping out</strong> latter. if you want to test your class and use a <strong>mock version</strong> of the <strong>dependency</strong> </p> <p>1.a. Will there be any problems with <strong>concurrent</strong> calls or multiple classes? specially in <code>JDBC static methods</code> for just an example?</p> <p>1.b. I think it would make too much <strong>memory load</strong> as a <strong>whole class would</strong> be <code>instanticated</code> many times just to call one or two methods</p></li> <li><p>Thats way over my head, do explain that and or any advantages/disadvantages</p></li> <li><p>I <strong>do Not</strong> want to <strong>use a framework</strong> in context to this question.. Thats way over my head, do explain that and or any advantages/disadvantages</p></li> <li><p>Awaiting any other strategies or recommendations, if any.</p></li> </ol> <p><strong><code>Request:</code> Please only answer if you are experienced and know the implications deeply and can comprehensively, with your answer, help me and the community as a whole!</strong></p> <p><strong><code>Code:</code></strong></p> <pre><code>/** The classes that implement a concrete strategy should implement this. * The Context class uses this to call the concrete strategy. */ interface Strategy { int execute(int a, int b); } /** Implements the algorithm using the strategy interface */ class Add implements Strategy { public int execute(int a, int b) { System.out.println("Called Add's execute()"); return a + b; // Do an addition with a and b } } class Subtract implements Strategy { public int execute(int a, int b) { System.out.println("Called Subtract's execute()"); return a - b; // Do a subtraction with a and b } } class Multiply implements Strategy { public int execute(int a, int b) { System.out.println("Called Multiply's execute()"); return a * b; // Do a multiplication with a and b } } // Configured with a ConcreteStrategy object and maintains // a reference to a Strategy object class Context { private Strategy strategy; public Context(Strategy strategy) { this.strategy = strategy; } public int executeStrategy(int a, int b) { return this.strategy.execute(a, b); } } /** Tests the pattern */ class StrategyExample { public static void main(String[] args) { Context context; // Three contexts following different strategies context = new Context(new Add()); int resultA = context.executeStrategy(3,4); context = new Context(new Subtract()); int resultB = context.executeStrategy(3,4); context = new Context(new Multiply()); int resultC = context.executeStrategy(3,4); System.out.println("Result A : " + resultA ); System.out.println("Result B : " + resultB ); System.out.println("Result C : " + resultC ); } } </code></pre>
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    1. COI would say that depends on the code of the method. What is it supposed to do? Is it [a command? A query?](http://en.wikipedia.org/wiki/Command%E2%80%93query_separation) An algorithm you might want to swap later with another one?
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    2. COupdated 2nd paragraph
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    3. COThat's not helpful. Example: If you want to swap the method with another one based on some configuration or similar, you may want to use a Strategy. If you simply want to make that method reusable, you might want to use a [Method Object](http://www.refactoring.com/catalog/replaceMethodWithMethodObject.html) (That's basically 1.b).
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