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123 lines
4.7 KiB
HTML
123 lines
4.7 KiB
HTML
<!DOCTYPE html>
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<meta name="author" content="Fredrik Danielsson, http://lostkeys.se">
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<article class="article">
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<h1>Lecture on March 22nd</h1>
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<h2>Method Documentation</h2>
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<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>
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<p>The Java API actually uses this technique to produce its own documentation.</p>
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<p>To create this, indicate a method with special comments that begin with <code>/**</code> and ends with <code>*/</code></p>
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<p>It contains <em>block tags</em> that describe input and output parameters</p>
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<p><code>@param</code> and <code>@return</code></p>
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<h3>Example</h3>
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<pre><code class="language-java">/**
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* @param y an integer to sum
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* @param x an integer to sum
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* @return the sum of x and y
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*/
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public int multiply(int x, int y) {
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return x + y;
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}</code></pre>
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<h2>Passing a Scanner</h2>
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<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>
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<p>If a method needs a scanner, you can pass the one you already created in as an input parameter.</p>
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<h2>Array as Input Parameter</h2>
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<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>
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<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>
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<pre><code class="language-java">public static void main(String[] args) {
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int[] nums = {1, 3, 5, 7, 9};
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timesTwo(nums);
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}
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public static void timesTwo(int[] arr) {
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for (int i = 0; i < arr.length; i++) {
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arr[i] *= 2;
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}
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}</code></pre>
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<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>
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<h2>Sizes of Arrays</h2>
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<h3>Perfect Size Arrays</h3>
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<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>
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<h3>Oversize Arrays</h3>
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<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>
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<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>
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<p>So we can create another variable, which will keep track of the index in where we can add the next element.</p>
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<p>We use oversized arrays when the size of the array is unknown or may change.</p>
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