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<!doctype html>
<html lang="en">
<head>
<meta http-equiv="x-ua-compatible" content="ie=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="Study guide for the Oracle Certified Professional, Java SE 8 Programmer Exam ">
<title>Java 8 Programmer II Study Guide: Exam 1Z0-809</title>
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<div class="header">
<div class="title-container">
<div class="chapter-title">
<h1><i class="chapter">Chapter TWENTY</i><br />
Assertions</h1>
<p><br /></p>
<h3 style="text-align: center;"><i>Exam Objectives</i></h3>
<p style="text-align: center;"><i>Test invariants by using assertions.</i><br /></p>
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<h2>Answers</h2>
<p><b>1. The correct answer is C.</b><br /> The <code>++</code> operator increments the value of <code>x</code> to <code>1</code> before the condition is evaluated. Note that changing values of variables or objects in assertions is discouraged since there's no guarantee that assertions would be enabled when the program runs.</p>
<p><br /></p>
<p><b>2. The correct answer is A.</b><br /> You can disable assertion at the command-line. The other statements are false.</p>
<p><br /></p>
<p><b>3. The correct answer is B.</b><br /> The command:<br />
<code class="hljs">java -esa -ea:com.example MainClass</code><br /> Enables assertions in system classes and classes in the <code>com.example</code> package.</p>
<p><br /></p>
<p><b>4. The correct answer is D.</b><br /> There's nothing wrong with the program, the method <code>isValid()</code> returns <code>false</code>, which makes the program to throw an <code>AssertionError</code> at runtime.</p>
<p><br /></p>
<p><b>5. The correct answer is B.</b><br />
<code class="hljs">assert false : "Assertion is false"</code><br /> Behaves in a similar way to:<br />
<code class="hljs">throw new AssertionError("Asssertion is false");</code><br/>
When assertions are enabled.</p>
<p><br /></p>
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