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Bradley Bickford 2024-05-14 19:10:20 -04:00
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40
CS2 - Demo/Main.java
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@ -1,55 +1,17 @@
import java.util.Scanner;
/*
CS2 Demo
System.out and System.in
This demo goes over how to write and read text
from the console so that we can have some basic input and
output from our Java program
*/
public class Main {
public static void main(String[] args) {
//System.out.println is used when you want
//to put some text into the console when your program is
//running. A lot of the time, you'll see the first
//programming example your trying to learn is
//a "Hello World!" example. System.out.println
//is one of many ways that you can output text
//to the console
System.out.println("Hello World!");
System.out.println("This is console out!");
//A Scanner is used together with System.in to collect
//text, numbers, true and false values, etc. from users
//of your program. While Scanner is not the only
//way of interacting with System.in, it's one of the
//more straightforward ways
Scanner scan = new Scanner(System.in);
//Notice that we use System.out.print and System.out.println
//here, the difference is one moves the text cursor to the
//next line after writing the text you asked for (println)
//and one doesn't (print)
System.out.print("Write some text: ");
//Scanner.nextLine() can be used to capture text
//from the user. Below, we combine some already written
//text with whatever the user ends up typing in. The nice
//thing about Scanner.nextLine() is that the program
//won't move forward until the user hits Enter on the
//keyboard
System.out.println("You wrote: " + scan.nextLine());
//Some resources, like Scanner, need to be closed. This
//"frees" the resource so that it's available for another part
//of this program (or another program running on the computer)
//to access it. In this case, because we're at the end of our
//program, closing Scanner isn't really necessary, but it's
//a good practice to get into, because there are some resources
//that need to be closed before your program finishes, otherwise
//you may "break" that resource for other programs.
scan.close();
}
}

41
CS3 - Demo/Main.java
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@ -1,42 +1,12 @@
import java.util.Scanner;
/*
CS3 Demo
Variables and Basic Math
This demo goes over how to store values in variables.
These values can be predefined in your code, come from
mathematical and other types of operations, or be collected
from the user in some way. This demo also covers general
math operations in Java
*/
public class Main {
public static void main(String[] args) {
//Below are some examples of program defined variables. Variables
//that you would set up in your code, and use elsewhere. There are 4 different
//types of variables here, all capable of storing different things.
//String = Text, int = Whole Numbers, double = decimal (real) numbers, boolean = true/false
//These are common variable types that you'll use in every Java program, but
//there are many other types of variables. Scanner, as we have also seen, is
//a type of variable.
//Notice the yellow lines under the variable names, this is just VSCode letting
//us know that the variables we've defined are never used, and therefore not needed
//They are here only for an example
String someString = "Some string value";
int lifeUniverseEverything = 42;
double someDouble = 2.22;
boolean bananasAreGood = true;
//Below are several examples on how to retrieve different types of values from the
//user. Strings, ints, booleans, and doubles can be grabbed using there appropriate
//method, nextLine for Strings, nextInt for ints, nextBoolean for booleans, and
//nextDouble for doubles. Each of these values are stored separately and then
//reprinted down below to the user.
//Notice how we can use the plus sign to combine other data types with Strings
//to be printed. Java is smart enough to know that those values need to be
//converted to String in order to combine properly. Just be careful, there
//are scenarios were this won't work.
Scanner scan = new Scanner(System.in);
System.out.print("Enter a string: ");
@ -57,15 +27,6 @@ public class Main {
System.out.println("Boolean: " + booleanValue);
System.out.println("Double: " + doubleValue);
//Below common math operations are displayed, you should be familiar with
//addition, multiplication, subtraction, and division already. But you may
//not be familiar with modulous or remainder operations (the % sign operation).
//This divides two integers (NOT DOUBLES) and rather than return the division result
//it returns the remainder, so rather than 5 / 3 = 1, you have 5 % 3 = 2
//Notice that the math operations are encased in parenthesis inside the
//call to System.out.println, this is done to ensure Java's automatic String combination
//mechanism doesn't get confused, and that our math operations are performed
//before trying to combine the result with the rest of the String.
System.out.print("Enter the first double value: ");
double firstNumber = scan.nextDouble();

41
CS5 - Demo/Main.java
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@ -1,55 +1,14 @@
import java.util.Random;
/*
CS5 Demo
For Loops and Random Numbers
This demo goes over how to write for loops and how
there generally used. This demo also includes Java's
Random class, so we can generate random values while using for
loops.
*/
public class Main {
public static void main(String[] args) {
//This for loop prints numbers from 0 through 9 (inclusive)
//A for loop in this instance does what is known as "iterating"
//over a series of values, in this case, we are iterating over
//a range of numbers. In order to use a for loop in this way
//we need to define three pieces inside the parenthesis
//int i = 0; This first piece (initialization) defines
//what value you are using to iterate your loop. This can
//actually be left out (unlike the next two pieces) if you're
//using a variable already defined elsewhere in your code
//i < 10; This is your condition, what determines if the loop
//should continue to run. So long as the variable i is < 10,
//the loop runs.
//i++ - This is our modifier, the thing that is changing to
//ensure that at some point our loop will exit (and avoid an
//infinite loop). i++ just means to add 1 to i. Each time the
//loop finishes a run of whatever is inside the brackets, i++
//will get called to update the value of i to i = i + 1;
//For this loop, all we're doing is printing the value of
//i as it changes while the loop runs.
for(int i = 0; i < 10; i++) {
System.out.println("Index Number: " + i);
}
//Similar to Scanner, we can create other types of objects
//and in this case, we are creating one called Random.
//This just gives us access to a (pseudo) random value generator.
//This wouldn't be good if you wanted truely random values, but
//it'll serve out purposes well enough for now.
Random random = new Random();
//With this for loop, we're trying to print 5 of each type of
//primitive value (int, double, and boolean) that we've seen so
//far. If all goes well, this will print the following for each
//variable type
//ValueName Value i+1: randomValue
//Where ValueName is the current random value type we're trying to create
//i is the current for loop i value
//randomValue is the value generated by the Random object for
//that specific type of variable.
for(int i = 0; i < 5; i++) {
System.out.println("Int Value " + (i + 1) + ": " + random.nextInt());
System.out.println("Double Value " + (i + 1) + ": " + random.nextDouble());