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content/ta/fall2017/cpsc220/sept25.md

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+# 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
+```
+