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169 lines
5.2 KiB
HTML
169 lines
5.2 KiB
HTML
<!DOCTYPE html>
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<meta name="author" content="Brandon Rozek">
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<title>Brandon Rozek</title>
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Courses
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Lab Aide
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Presentations
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Research
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Transcript
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<main class="main-content">
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<article class="article">
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<h1>Lecture for January 23</h1>
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<h2>Java Class</h2>
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<p>In Java, your code must live in a class.</p>
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<pre><code class="language-java">public class NameOfClass {
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public static void main(String[] args) {
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// All program code
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}
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}</code></pre>
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<p>It is important that <code>NameOfClass</code> is named meaningfully for the code. It is convention to use CamelCase when using classes. (Capitalize your class names!)</p>
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<p>All methods have a method signature, it is unique to it. For main it is the words <code>public static void</code> and the argument <code>String[] args</code>.</p>
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<p><code>public</code> means that any other piece of code can reference it.</p>
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<p><code>void</code> means that the method returns nothing</p>
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<p><code>main</code> is the name of the method. It is important to have <code>main</code> since that tells the Java Interpreter where to start in your program.</p>
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<p><code>String[] args</code> is the command line arguments inputted into the program. For this part of the class, we don't need to worry about it.</p>
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<p>If you noticed <code>String</code> is a class, it is not a primitive type. This is denoted in Java by having it capitalized.</p>
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<h2>Arithmetic Expressions</h2>
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<p>There is an order of operations in programming as well. It goes like this:</p>
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<ol>
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<li>Parenthesis</li>
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<li>Unary Operations</li>
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<li>*, /, %</li>
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<li>+, -</li>
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</ol>
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<p>And from there you read from left to right.</p>
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<h2>Constant Variables</h2>
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<p>These are variables that can never be changed</p>
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<pre><code class="language-java">final int MINUTES_PER_HOUR = 60</code></pre>
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<p>The keyword <code>final</code> indicates to the Java compiler that it is a constant variable.</p>
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<p>By convention, constants are in all caps with underscores being separated between the words</p>
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<h2>Java Math Library</h2>
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<p>There are some arithmetic expressions that we want to be able to do and we cannot achieve that simply with the standard operations</p>
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<table>
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<thead>
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<tr>
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<th>Method</th>
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<th>Description</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>Math.sqrt(x)</td>
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<td>square root</td>
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</tr>
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<tr>
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<td>Math.abs(x)</td>
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<td>absolute value</td>
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</tr>
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<tr>
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<td>Math.pow(a, b)</td>
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<td>exponentiation $a^b$</td>
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</tr>
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<tr>
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<td>Math.max(a, b)</td>
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<td>returns the maximum of a or b</td>
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</tr>
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<tr>
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<td>Math.min(a, b)</td>
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<td>returns the minimum of a or b</td>
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</tr>
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<tr>
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<td>Math.round(x)</td>
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<td>rounds to the nearest integer</td>
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</tr>
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</tbody>
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</table>
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<h2>Example: Finding Areas</h2>
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<pre><code class="language-java">public class MoreVariables
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public static void main(String[] args) {
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// Decrate a variable
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int x;
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// Initialize ia variable
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x = 5;
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// Area of a square
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int squareArea = x * x;
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System.out.println("Area of a square: " + squareArea);
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double newSquare = Math.pow(x, 2);
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System.out.println("Area of square: " + newSquare);
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// Area of Circle
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final double PI = 3.14159;
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double radius = 3;
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double circleArea = radius * radius * PI;
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System.out.println("Area of circle: " + circleArea);
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}</code></pre>
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</article>
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