website/static/~brozek/index.html?labaide%2Fspring2018%2Fcpsc220%2Fmar22.html

123 lines
4.7 KiB
HTML

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="author" content="Fredrik Danielsson, http://lostkeys.se">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="robots" content="noindex" />
<title>Brandon Rozek</title>
<link rel="stylesheet" href="themes/bitsandpieces/styles/main.css" type="text/css" />
<link rel="stylesheet" href="themes/bitsandpieces/styles/highlightjs-github.css" type="text/css" />
</head>
<body>
<aside class="main-nav">
<nav>
<ul>
<li class="menuitem ">
<a href="index.html%3Findex.html" data-shortcut="">
Home
</a>
</li>
<li class="menuitem ">
<a href="index.html%3Fcourses.html" data-shortcut="">
Courses
</a>
</li>
<li class="menuitem ">
<a href="index.html%3Flabaide.html" data-shortcut="">
Lab Aide
</a>
</li>
<li class="menuitem ">
<a href="index.html%3Fpresentations.html" data-shortcut="">
Presentations
</a>
</li>
<li class="menuitem ">
<a href="index.html%3Fresearch.html" data-shortcut="">
Research
</a>
</li>
<li class="menuitem ">
<a href="index.html%3Ftranscript.html" data-shortcut="">
Transcript
</a>
</li>
</ul>
</nav>
</aside>
<main class="main-content">
<article class="article">
<h1>Lecture on March 22nd</h1>
<h2>Method Documentation</h2>
<p>Java has a special way that you can document your methods such that it will create documentation for you if you follow the convention.</p>
<p>The Java API actually uses this technique to produce its own documentation.</p>
<p>To create this, indicate a method with special comments that begin with <code>/**</code> and ends with <code>*/</code></p>
<p>It contains <em>block tags</em> that describe input and output parameters</p>
<p><code>@param</code> and <code>@return</code></p>
<h3>Example</h3>
<pre><code class="language-java">/**
* @param y an integer to sum
* @param x an integer to sum
* @return the sum of x and y
*/
public int multiply(int x, int y) {
return x + y;
}</code></pre>
<h2>Passing a Scanner</h2>
<p>We only want to create one <strong>user input scanner</strong> per program, we also only want one <strong>file input scanner</strong> per program.</p>
<p>If a method needs a scanner, you can pass the one you already created in as an input parameter.</p>
<h2>Array as Input Parameter</h2>
<p>Primitive types (<code>int</code>, <code>char</code>, <code>double</code>, etc.) are passed by value. Modifications made inside a method cannot be seen outside the method.</p>
<p>Arrays on the other hand, is pass by reference. Changes made to an array inside the method can be seen outside the method.</p>
<pre><code class="language-java">public static void main(String[] args) {
int[] nums = {1, 3, 5, 7, 9};
timesTwo(nums);
}
public static void timesTwo(int[] arr) {
for (int i = 0; i &lt; arr.length; i++) {
arr[i] *= 2;
}
}</code></pre>
<p>At the end of the <code>timesTwo</code> method call, the variable <code>nums</code> would have <code>{2, 6, 10, 14, 18}</code></p>
<h2>Sizes of Arrays</h2>
<h3>Perfect Size Arrays</h3>
<p>When we declare an array, Java automatically fills every slot of the array with the type in memory. So if you know that you need exactly 8 slots, then you only ask for 8.</p>
<h3>Oversize Arrays</h3>
<p>This is when we don't know how many slots we need. Therefore, we ask for more than we think we'll need. That way we don't go out of bounds.</p>
<p>If we do this, then we don't know how many elements we have already inserted into the array. Since the length is the number of slots.</p>
<p>So we can create another variable, which will keep track of the index in where we can add the next element.</p>
<p>We use oversized arrays when the size of the array is unknown or may change.</p>
</article>
</main>
<script src="themes/bitsandpieces/scripts/highlight.js"></script>
<script src="themes/bitsandpieces/scripts/mousetrap.min.js"></script>
<script type="text/x-mathjax-config">
MathJax.Hub.Config({
tex2jax: {
inlineMath: [ ['$','$'], ["\\(","\\)"] ],
processEscapes: true
}
});
</script>
<script type="text/javascript"
src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>
<script>
hljs.initHighlightingOnLoad();
document.querySelectorAll('.menuitem a').forEach(function(el) {
if (el.getAttribute('data-shortcut').length > 0) {
Mousetrap.bind(el.getAttribute('data-shortcut'), function() {
location.assign(el.getAttribute('href'));
});
}
});
</script>
</body>
</html>