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POJava unchecked/checked exception clarification
 

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  1. POJava unchecked/checked exception clarification
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    <p>I've been reading about unchecked versus checked questions, none of the online resources have been truly clear about the difference and when to use both.</p> <p>From what I understand, both of them get thrown at runtime, both of them represent program states that are outside the expected bounds of the logic, but checked exceptions must be explicitly caught while unchecked ones do not.</p> <p>My question is, suppose for argument's sake I have a method that divides two numbers</p> <pre><code>double divide(double numerator, double denominator) { return numerator / denominator; } </code></pre> <p>and a method that requires divison somewhere</p> <pre><code>void foo() { double a = divide(b, c); } </code></pre> <p>Who is responsible for checking the case of the denominator being zero, and should an exception be checked or unchecked (ignoring Java's built in divison checks)?</p> <p>So, would the divide method be declared as is or as</p> <pre><code>double divide(double numerator, double denominator) throws DivideByZeroException { if(denominator == 0) throw DivideByZeroException else ... } void foo() { try{ double a = divide(b, c); } catch(DivideByZeroException e) {} } </code></pre> <p>or without a checked exception, as is:</p> <pre><code>double divide(double numerator, double denominator) { if(denominator == 0) throw DivideByZeroException else ... } void foo() { if(c != 0) double a = divide(b, c); } </code></pre> <p>and allow foo to make the divide by zero check?</p> <p>This problem originally arose in a mathematical program I wrote in which users entered numbers and logic classes performed calculations. I was never sure whether the GUI should check immediately for improper values, or whether the internal logic should catch them during calculation and throw exceptions.</p>
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    1. COI can elaborate on the topic but the whole example is entirely wrong: because? Only integer division by zero results in an exception. Floating point one (double incl) results either in some infinity (neg/pos) or a "simple" NaN (in case of 0/0)
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    2. COYou're right, and I said to ignore java's default division checks and assume for argument's sake that we want to treat division by zero as an error (which it happens to be in my original program).
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    3. COthat's not related to the exception handling but *do not* checkd double==0, it may not work properly for values close but not equal (==) zero. Floating point division by zero is not an error by design. Most of the code should be able to properly handle infinity/nan and deal with such cases. So in your case you need smth like `if (Math.abs(denominator)<EPSILON)...` and define EPSILON with the precision you need, e.g `EPSILON = 1e-12`.
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