mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-12-04 21:03:16 -05:00
297 lines
8 KiB
HTML
297 lines
8 KiB
HTML
<!DOCTYPE html>
|
|
<html>
|
|
<head>
|
|
<meta charset="utf-8" />
|
|
<meta name="author" content="Brandon Rozek">
|
|
<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>CPSC 220 Lecture 3</h1>
|
|
<h2>Variables</h2>
|
|
<p>Variable -- Storage of information</p>
|
|
<p>The type cannot change in a variable.</p>
|
|
<p>Examples of types include</p>
|
|
<ul>
|
|
<li>int</li>
|
|
<li>float</li>
|
|
<li>double</li>
|
|
<li>String</li>
|
|
<li>char</li>
|
|
<li>boolean</li>
|
|
</ul>
|
|
<p>Declaration: <code>int num;</code></p>
|
|
<p>Initialization: <code>num = 5;</code></p>
|
|
<p>Declaration + Initialization: <code>int num = 5;</code></p>
|
|
<h3>Possible Errors</h3>
|
|
<p><strong>You cannot declare a variable multiple times.</strong></p>
|
|
<p>Undefined variables are when you do not declare a variable before attempting to use it.</p>
|
|
<h3>Casting</h3>
|
|
<p>You need to cast if you are attempting to lose data or store a larger memory type into a smaller one.</p>
|
|
<p>double -> float -> int <strong>(casting required)</strong></p>
|
|
<pre><code class="language-java">double gpa = 3.2;
|
|
int num1 = 10 * (int)gpa // 30</code></pre>
|
|
<h1>Operations</h1>
|
|
<p>The basic number operations are</p>
|
|
<ul>
|
|
<li>+</li>
|
|
<li>-</li>
|
|
<li>*</li>
|
|
<li>/</li>
|
|
<li>% <em>(the remainder)</em></li>
|
|
</ul>
|
|
<p>Examples</p>
|
|
<pre><code class="language-java">0 % 2 // 0
|
|
1 % 2 // 1
|
|
2 % 2 // 0
|
|
|
|
3 % 2 // 1
|
|
4 % 2 // 0
|
|
5 % 2 // 1
|
|
|
|
3 % 5 // 3
|
|
7 % 5 // 2</code></pre>
|
|
<p>You can test if something is even using modulus %</p>
|
|
<pre><code class="language-java">// Assuming i was initiliazed to a value earlier
|
|
if (i % 2 == 0) {
|
|
System.out.println("i is even");
|
|
} else {
|
|
System.out.println("i is odd");
|
|
}</code></pre>
|
|
<h1>System input</h1>
|
|
<p>Here is sample code using a Scanner as input</p>
|
|
<pre><code class="language-java">import java.util.Scanner;
|
|
public class ScannerExample {
|
|
public static void main(String[] args) {
|
|
Scanner in;
|
|
in = new Scanner(System.in);
|
|
|
|
// Grab numerical values
|
|
int num = in.nextInt();
|
|
float gpa = in.nextFloat();
|
|
double weight = in.nextDouble();
|
|
|
|
// Grab a single character
|
|
in.nextLine()
|
|
char initial = in.next().charAt(0);
|
|
|
|
// To get the entire line of a string
|
|
in.nextLine();
|
|
String name = in.nextLine();
|
|
}
|
|
}</code></pre>
|
|
<p>You need to use <code>in.nextLine()</code> to grab the carriage return that is left after grabbing a numeric value.</p>
|
|
<h1>Classes and Objects</h1>
|
|
<p>Classes are a new type that you can have multiple things of.</p>
|
|
<p>These classes are blueprints that are made up of primitives or more basic types.</p>
|
|
<p>First create a Pet.java file (Name of the class must match the name of the file)</p>
|
|
<pre><code class="language-java">public class Pet {
|
|
private String name;
|
|
private int years;
|
|
}</code></pre>
|
|
<p>You can then use the Pet class in your main program. The terminology here is that you can create instances or objects of the class.</p>
|
|
<p>In PetTester.java</p>
|
|
<pre><code class="language-java">public class PetTester {
|
|
public static void main(String[] args) {
|
|
Pet myPet;
|
|
myPet = new Pet();
|
|
}
|
|
}</code></pre>
|
|
<p><strong>Both Pet.java and PetTester.java must be in the same directory/folder</strong></p>
|
|
<h3>Mutators/Accessors</h3>
|
|
<p>Since the variables are private we cannot access them in the main program. To work around this, we can write what is called a mutator method.</p>
|
|
<pre><code class="language-java">public class Pet {
|
|
private String name;
|
|
private int years;
|
|
|
|
// Mutators
|
|
public void setName(String n) {
|
|
name = n;
|
|
}
|
|
public void setYears(int y) {
|
|
if (y >= 0) {
|
|
years = y;
|
|
} else {
|
|
System.out.println("No one is less than 0 years old.")
|
|
}
|
|
}
|
|
}</code></pre>
|
|
<p>Now let's use these new methods</p>
|
|
<pre><code class="language-java">public class PetTester {
|
|
public static void main(String[] args) {
|
|
Pet mypet;
|
|
myPet = new Pet();
|
|
myPet.setName("Fred");
|
|
myPet.setAge(20);
|
|
}
|
|
}</code></pre>
|
|
<p>We need a method that will allow us to access the data type. Let's add accessors to our pet class.</p>
|
|
<pre><code class="language-java">public class Pet {
|
|
private String name;
|
|
private int years;
|
|
|
|
// Mutators
|
|
public void setName(String n) {
|
|
name = n;
|
|
}
|
|
public void setYears(int y) {
|
|
if (y >= 0) {
|
|
years = y;
|
|
} else {
|
|
System.out.println("No one is less than 0 years old.")
|
|
}
|
|
}
|
|
|
|
// Accessors
|
|
public String getName() {
|
|
return name;
|
|
}
|
|
public int getYears() {
|
|
return years;
|
|
}
|
|
}</code></pre>
|
|
<p>Now let's get some information from the pet object, such as the age.</p>
|
|
<pre><code class="language-java">public class PetTester {
|
|
public static void main(String[] args) {
|
|
Pet mypet;
|
|
myPet = new Pet();
|
|
myPet.setName("Fred");
|
|
myPet.setYears(20);
|
|
|
|
int year = myPet.getYears();
|
|
}
|
|
}</code></pre>
|
|
<h3>Constructors</h3>
|
|
<p>Constructors lets us initialize variables in the class without having to use mutator methods.</p>
|
|
<pre><code class="language-java">public class Pet {
|
|
private String name;
|
|
private int years;
|
|
|
|
// Default Constructor
|
|
public Pet() {
|
|
name = "";
|
|
years = 0;
|
|
}
|
|
// Non-Default Constructor
|
|
public Pet(int y, String n) {
|
|
name = n;
|
|
years = y;
|
|
}
|
|
|
|
// Mutator Methods
|
|
public void setName(String n) {
|
|
name = n;
|
|
}
|
|
public void setYears(int y) {
|
|
if (y >= 0) {
|
|
years = y;
|
|
} else {
|
|
System.out.println("No one is less than 0 years old.")
|
|
}
|
|
}
|
|
|
|
// Accessor Methods
|
|
public String getName() {
|
|
return name;
|
|
}
|
|
public int getYears() {
|
|
return years;
|
|
}
|
|
}</code></pre>
|
|
<p>Now let us see this in action.</p>
|
|
<pre><code class="language-java">public class PetTester {
|
|
public static void main(String[] args) {
|
|
Pet yourPet = new Pet(10, "Fluffy");
|
|
}
|
|
}</code></pre>
|
|
<p>You can have as many constructors as you want, but they must be different.</p>
|
|
<p>Example:</p>
|
|
<pre><code class="language-java">public class Pet {
|
|
...
|
|
pet() {
|
|
name = "";
|
|
years = 0;
|
|
}
|
|
pet(int y, String n) {
|
|
name = n;
|
|
years = y;
|
|
}
|
|
pet(String n) {
|
|
years = 1;
|
|
name = n;
|
|
}
|
|
...
|
|
}</code></pre>
|
|
</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>
|