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<h1>LiquidJava Quiz</h1>

<p>Test your knowledge about LiquidJava concepts including refinements, object state modeling and ghost variables!</p>

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<p>Liquid types allow developers to catch bugs at:</p>

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<li><label><input type="radio" data-question="1" data-content="0" /> Execution time</label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> Compile time</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> Deployment time</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> Testing time</label></li>

<p>Liquid types can prevent which of the following bugs? <strong>(Select all that apply)</strong> </p>

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<li><label><input type="checkbox" data-question="0" data-content="1" /> Array index out-of-bounds</label></li>

<li><label><input type="checkbox" data-question="0" data-content="1" /> Null pointer exceptions</label></li>

<li><label><input type="checkbox" data-question="1" data-content="0" /> Memory leaks</label></li>

<li><label><input type="checkbox" data-question="0" data-content="1" /> Division by zero</label></li>

<p>In LiquidJava, what integer values for <code>x</code> are allowed with this refinement? <code>@Refinement("x &gt; 0")</code></p>

<ul class="radio-list">

<li><label><input type="radio" data-question="1" data-content="0" /> All values</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> All negative values</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> All non-negative values</label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> All positive values</label></li>

<p>In LiquidJava, which of the following can be refined? <strong>(Select all that apply)</strong></p>

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<li><label><input type="checkbox" data-question="0" data-content="1" /> Variables</label></li>

<li><label><input type="checkbox" data-question="0" data-content="1" /> Parameters</label></li>

<li><label><input type="checkbox" data-question="0" data-content="1" /> Return values</label></li>

<li><label><input type="checkbox" data-question="1" data-content="0" /> Imports</label></li>

<p>In LiquidJava, which of the following is <strong>not</strong> a valid refinement?</p>

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<li><label><input type="radio" data-question="1" data-content="0" /> <code>@Refinement("x == 1 || x == -1")</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@Refinement("x &gt; 0")</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@Refinement("x % 2 == 0")</code></label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> <code>@Refinement("x + 1")</code></label></li>

<p>In LiquidJava, to specify that a method should only be called when the object is in a certain state, we should use a:</p>

<ul class="radio-list">

<li><label><input type="radio" data-question="0" data-content="1" /> <code>@StateRefinement</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@Refinement</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@RefinementAlias</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@RefinementPredicate</code></label></li>

<p>In LiquidJava, what does the following state refinement mean? <code>@StateRefinement(from="!closed(this)", to="closed(this)")</code></p>

<ul class="radio-list">

<li><label><input type="radio" data-question="1" data-content="0" /> The method can only be called when the object is closed and will leave it closed</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> The method can only be called when the object is open and will leave it open</label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> The method can only be called when the object is not closed and will leave it closed</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> The method can be called in any state and will leave it closed</label></li>

<p>In LiquidJava, the <code>@ExternalRefinementsFor</code> annotation is used to:</p>

<ul class="radio-list">

<li><label><input type="radio" data-question="1" data-content="0" /> Import refinements from external libraries</label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> Define new refinements for an external class or interface</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> Export refinements to other modules</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> None of the above</label></li>

<p>In LiquidJava, a ghost variable is used to:</p>

<ul class="radio-list">

<li><label><input type="radio" data-question="1" data-content="0" /> Store temporary data during the program execution</label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> Model abstract properties of objects for verification purposes</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> Track memory usage of the program</label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> Replace regular variables for better performance</label></li>

<p>In LiquidJava, which of the following refinements updates the ghost variable <code>size</code>?</p>

<ul class="radio-list">

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@Refinement("size = 0")</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@StateRefinement(from="size(this) > 0")</code></label></li>

<li><label><input type="radio" data-question="1" data-content="0" /> <code>@Refinement("size == 0")</code></label></li>

<li><label><input type="radio" data-question="0" data-content="1" /> <code>@StateRefinement(to="size(this) == size(old(this)) + 1")</code></label></li>

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