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POInvoking a method overloaded where all arguments implement the same interface
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  1. POInvoking a method overloaded where all arguments implement the same interface
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    copied!<p>My starting point is the following:<br> - I have a method, transform, which I overloaded to behave differently depending on the type of arguments that are passed in (see transform(A a1, A a2) and transform(A a1, B b) in my example below)<br> - All these arguments implement the same interface, X</p> <p>I would like to apply that transform method on various objects all implementing the X interface.</p> <p>What I came up with was to implement transform(X x1, X x2), which checks for the instance of each object before applying the relevant variant of my transform.</p> <p>Though it works, the code seems ugly and I am also concerned of the performance overhead for evaluating these various instanceof and casting. Is that transform the best I can do in Java or is there a more elegant and/or efficient way of achieving the same behavior?</p> <p>Below is a trivial, working example printing out BA. I am looking for examples on how to improve that code. In my real code, I have naturally more implementations of 'transform' and none are trivial like below.</p> <pre><code>public class A implements X { } public class B implements X { } interface X { } public A transform(A a1, A a2) { System.out.print("A"); return a2; } public A transform(A a1, B b) { System.out.print("B"); return a1; } // Isn't there something better than the code below??? public X transform(X x1, X x2) { if ((x1 instanceof A) &amp;&amp; (x2 instanceof A)) { return transform((A) x1, (A) x2); } else if ((x1 instanceof A) &amp;&amp; (x2 instanceof B)) { return transform((A) x1, (B) x2); } else { throw new RuntimeException("Transform not implemented for " + x1.getClass() + "," + x2.getClass()); } } @Test public void trivial() { X x1 = new A(); X x2 = new B(); X result = transform(x1, x2); transform(x1, result); } </code></pre>
 

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