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copied!<p>In general, Java generics are not appropriate for math.</p> <p>In Java:</p> <ul> <li>Generics are object only.</li> <li>There are no mathematical operators for objects.</li> </ul> <p>It looks like you can perform math on objects because you can do something like this:</p> <pre><code>Integer a = 1; Integer b = 2; Integer c = a + b; </code></pre> <p>But that is only due to autoboxing. What actually happens is the compiler replaces that code with this:</p> <pre><code>Integer a = new Integer(1); Integer b = new Integer(3); Integer c = Integer.valueOf(a.intValue() + b.intValue()); </code></pre> <p>With generics you can specify a bound so that your type must be Number or a subtype of it:</p> <pre><code>static <N extends Number> N multiply(N n1, N n2) { return n1 * n2; // but you cannot do this because the type is not known // so the compiler cannot do autoboxing } </code></pre> <p>If a supertype is known, you <em>can</em> call methods on them so you can do this as has been pointed out:</p> <pre><code>static <N extends Number> double multiply(N n1, N n2) { return n1.doubleValue() * n2.doubleValue(); } </code></pre> <p>But that is no different than the following:</p> <pre><code>static double multiply(double n1, double n2) { return n1 * n2; } </code></pre> <p>Except that the generic version can, for example, take BigDecimal as an argument which will of course not provide a reliable result (see <a href="http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html#doubleValue%28%29" rel="nofollow">BigDecimal#doubleValue</a>). (Neither will Long for that matter.)</p> <p>If you were really determined you could program your own number classes and use polymorphism. Otherwise use overloads or (best of all) stick to one type.</p>

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