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ch14a.html
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ch14a.html
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<!doctype html>
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<title>Java 8 Programmer II Study Guide: Exam 1Z0-809</title>
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<h1><i class="chapter">Chapter FOURTEEN</i><br />
Optional Class</h1>
<p><br /></p>
<h3 style="text-align: center;"><i>Exam Objectives</i></h3>
<p style="text-align: center;"><i>Develop code that uses the Optional class.</i><br /></p>
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<h2>Answers</h2>
<p><b>1. The correct answer is C.</b><br /> The method <code>orElseGet()</code> returns a value of the type of the <code>Optional</code>, it doesn't return an exception, no matter if it's not executed. For exceptions, we have to use <code>orElseThrow()</code>.</p>
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<p><b>2. The correct answer is C.</b><br /> Option A is false. The method <code>Optional.ifPresent()</code> is the one that takes a <code>Consumer<T></code> as an argument that is executed only if the <code>Optional</code> contains a value.<br /> Option B is false. The method <code>Optional.of()</code> cannot create an empty <code>Optional</code>.<br /> Option C is true. The method <code>Optional.of()</code> can throw a <code>NullPointerException</code> if its argument is <code>null</code>.<br /> Option D is false. The method <code>Optional.ifPresent()</code> takes a <code>Consumer<T></code> as an argument.</p>
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<p><b>3. The correct answer is D.</b><br /> The program is passing an invalid number to the method, so an exception is thrown by <code>Integer.parseInt()</code> and <code>Optional.empty</code> is returned. The method <code>get()</code> throws an exception if the <code>Optional</code> has an empty value, and this is exactly what happens.</p>
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<p><b>4. The correct answer is A.</b><br /> The <code>orElse()</code> method returns the argument when the <code>Optional</code> is empty, otherwise, it returns the encapsulated value of the <code>Optional</code>, in this case, <code>0</code>.</p>
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