mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-21 15:56:29 -05:00
239 lines
7.6 KiB
HTML
239 lines
7.6 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 4</h1>
|
||
<h2>Practice Problem</h2>
|
||
<ol>
|
||
<li>Create a class called Car</li>
|
||
<li>
|
||
<ul>
|
||
<li>Create a private variable of int type called year</li>
|
||
<li>Create a private variable of String type called make</li>
|
||
</ul>
|
||
</li>
|
||
<li>Create accessor methods for all data members.</li>
|
||
<li>Create mutator methods for all data methods.</li>
|
||
</ol>
|
||
<pre><code class="language-java">public class car { // begin car
|
||
private int year;
|
||
private String make;
|
||
public int getYear(void) {
|
||
return year;
|
||
}
|
||
public String getMake() {
|
||
return make;
|
||
}
|
||
public void setYear(int y) {
|
||
if (y > 1890) {
|
||
year = y;
|
||
} else {
|
||
System.out.println(y + " is not a valid year.");
|
||
}
|
||
}
|
||
public void setMake(String m) {
|
||
make = m;
|
||
}
|
||
}</code></pre>
|
||
<p>Local variables are only existent within the curly braces that it is defined in.</p>
|
||
<h2>If Statements and Boolean Expressions</h2>
|
||
<p>Boolean expressions return a boolean</p>
|
||
<pre><code class="language-java">1 < 4; // 1 is less than 4: TRUE
|
||
3 > 5; // 3 is greater than 5: FALSE
|
||
5 == 5; // 5 is equal to 5: TRUE
|
||
5 != 5; // 5 is not equal to 5: FALSE
|
||
1 >= 1; // 1 is greater than or equal to 1: TRUE
|
||
5 <= 1; // 5 is less than or equal to 1: FALSE</code></pre>
|
||
<p>If statements only occur if the boolean expression is true, otherwise the <code>else</code> block is executed.</p>
|
||
<pre><code class="language-java">if (true) {
|
||
System.out.println("I am always printed");
|
||
} else {
|
||
System.out.println("I am never printed");
|
||
}</code></pre>
|
||
<p>You can only have one <code>else</code> per <code>if</code>. If you have an <code>if</code> you don't necessarily need an <code>else</code></p>
|
||
<h2>Local vs Class Variables</h2>
|
||
<p>If you have a local variable and the class variable sharing the same name, then the local variable is always used first.</p>
|
||
<pre><code class="language-java">public class car { // begin car
|
||
private int year;
|
||
public void setYear(int year) {
|
||
year = year;
|
||
}
|
||
}</code></pre>
|
||
<p>This is a redundant statement, it makes the argument that is passed in equal to itself.</p>
|
||
<p>To avoid this situation, use the keyword <code>this</code> to access the class variable</p>
|
||
<pre><code class="language-java">public class car {
|
||
private int year;
|
||
public void setYear(int year) {
|
||
this.year = year;
|
||
}
|
||
}</code></pre>
|
||
<p>The code above runs as expected.</p>
|
||
<p>Rewriting our class with <code>this</code></p>
|
||
<pre><code class="language-java">public class car { // begin car
|
||
private int year;
|
||
private String make;
|
||
public int getYear(void) {
|
||
return year;
|
||
}
|
||
public String getMake() {
|
||
return make;
|
||
}
|
||
public void setYear(int year) {
|
||
if (y > 1890) {
|
||
this.year = year;
|
||
} else {
|
||
System.out.println(y + " is not a valid year.");
|
||
}
|
||
}
|
||
public void setMake(String make) {
|
||
this.make = make;
|
||
}
|
||
}</code></pre>
|
||
<h2>Unreachable Code</h2>
|
||
<p>When the code hits a <code>return</code> statement, it stops executing the rest of the code in the method. Also throws an Unreachable Code Error.</p>
|
||
<pre><code class="language-java">public int add(int x, int y) {
|
||
return x + y;
|
||
System.out.println("x + y = " + x + y);
|
||
}
|
||
add();
|
||
System.out.println("Hello");</code></pre>
|
||
<p>Here the code above will not compile, though assuming the error doesn't exist then it would only print out "Hello"</p>
|
||
<h2>Constructors</h2>
|
||
<p>You cannot have a private or protected constructors.</p>
|
||
<p>Constructors are used to initialize your objects.</p>
|
||
<p>You want to have the class variables to the left of the assignment statement.</p>
|
||
<pre><code class="language-java">public class car {
|
||
private int year;
|
||
private String make;
|
||
car() {
|
||
year = 1890;
|
||
make = "Ford";
|
||
}
|
||
car(int year, String make) {
|
||
this.year = year;
|
||
this.make = make;
|
||
}
|
||
}</code></pre>
|
||
<h2>Testers</h2>
|
||
<p>Testers are useful to check that the class is implemented correctly. Both the tester and the class have to be in the same folder/directory.</p>
|
||
<pre><code class="language-java">public class carTester {
|
||
public static void main(String[] args) {
|
||
Car myCar; // Declaration
|
||
myCar = new Car(); // Initilization
|
||
Car yourCar = new Car(2009, "Hyundai"); // Declaration + Initialization
|
||
}
|
||
}</code></pre>
|
||
<h2>More about classes</h2>
|
||
<pre><code class="language-java">public class Car {
|
||
private String name;
|
||
private int odometer;
|
||
public void setOdometer(int od) {
|
||
odometer = od;
|
||
}
|
||
public void setName(String n) {
|
||
this.name = n;
|
||
}
|
||
public void changeOilRequest(String name, int od) {
|
||
if (name == this.name) {
|
||
int difference = od - this.odometer;
|
||
if (difference > = 3000) {
|
||
// You can call other methods in the class
|
||
setOdo(od); // Equivalent to "this.setOdo(od);"
|
||
this.odometer = od;
|
||
System.out.println("Ready for oil change.");
|
||
} else {
|
||
System.out.println(name + " not ready for oil change.")
|
||
}
|
||
} // end if
|
||
} // end changeOil request
|
||
} // end class</code></pre>
|
||
<p>To call public methods outside the class use the variable name to do so.</p>
|
||
<pre><code class="language-java">public class CarTester {
|
||
public static void main(String[] args) {
|
||
Car myCar = new Car();
|
||
myCar.setName("Honda")
|
||
myCar.changeOilRequest("Honda", 3400);
|
||
}
|
||
}</code></pre>
|
||
<h2>Math library</h2>
|
||
<p>The <code>ceil</code> method rounds up while the <code>floor</code> method runs down.</p>
|
||
<pre><code class="language-java">Math.ceil(3.2); // 4
|
||
Math.ceil(4.1); // 4</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>
|