mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-13 20:27:29 -05:00
97 lines
1.8 KiB
Markdown
97 lines
1.8 KiB
Markdown
# Lecture in CPSC 220 Sept 25 2017
|
|
|
|
## Constants
|
|
|
|
Adding the keyword `final` in front of a variable declaration makes the variable constant. Meaning you cannot later change it in the code.
|
|
|
|
```java
|
|
final int MAX = 10;
|
|
```
|
|
|
|
By industry norm, the style of the variable is to have it in all caps.
|
|
|
|
You CANNOT do the following
|
|
|
|
```java
|
|
final int MAX = 10;
|
|
MAX = 15;
|
|
```
|
|
|
|
|
|
|
|
## Using Libraries
|
|
|
|
1. Import the library
|
|
2. Find the method that is appropriate
|
|
3. Use it
|
|
|
|
Example:
|
|
|
|
```java
|
|
import java.util.Math;
|
|
public class MathTest {
|
|
public static void main(String[] args) {
|
|
double answer = Math.ceil(5.4);
|
|
System.out.println(Math.ceil(4.5));
|
|
}
|
|
}
|
|
```
|
|
|
|
## Typecasting / Type Conversions
|
|
|
|
You can only cast a variable if you are casting it to a type that is larger than the one it was previously. The expression Polack used is that you cannot fit into super skinny jeans, but you can fit into bigger pants.
|
|
|
|
```java
|
|
double dnum;
|
|
float fnum;
|
|
int inum;
|
|
dnum = (double)fnum * (double)inum;
|
|
```
|
|
|
|
## Char vs String
|
|
|
|
`String`s are initialized in Java with double quotes while `char`s are initialized with single quotes
|
|
|
|
```java
|
|
char initial = 'j';
|
|
String name = "Jennifer";
|
|
```
|
|
|
|
Characters can be read in as an integer.
|
|
|
|
|
|
|
|
## Random Numbers
|
|
|
|
1. Import `java.util.Random;`
|
|
2. Declare the random number generator
|
|
3. Initialize with `new`
|
|
4. Use it
|
|
|
|
|
|
|
|
```java
|
|
import java.util.Random;
|
|
public class RandTest {
|
|
public static void main(String[] args) {
|
|
Random rand;
|
|
rand = new Random();
|
|
int number = rand.nextInt(100); // Random generates number between 0-99
|
|
}
|
|
}
|
|
```
|
|
|
|
How do you generate numbers in a different range? [50, 150]
|
|
|
|
```java
|
|
rand.nextInt(100); // 0-99
|
|
rand.nextInt(101) // 0 - 100
|
|
rand.nextInt(101) + 50 //50-150
|
|
```
|
|
|
|
In more general terms
|
|
|
|
```java
|
|
rand.nextInt(end - start + 1) + start
|
|
```
|
|
|