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content/ta/fall2017/cpsc220/dec6.md

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+# Final Review December 6
+
+## Classes
+
+Here is how you can create a class called "Employee" with a non-default constructor (a constructor that takes parameters) and a getter and setter
+
+```java
+public class Employee {
+  // Our private variables
+  private String name;
+  private double salary;
+  // Non-default constructor
+  public Employee(String name, double salary) {
+    this.name = name;
+    this.salarly = salary;
+  }
+  // This is a getter
+  public string getName() {
+    return name;
+  }
+  public double setSalarly(double salary) {
+    this.salary = salary;
+  }
+}
+```
+
+## For Loops + Arrays
+
+For loops are constructed in the following way
+
+`for (initialization; condition to stop; increment to get closer to condition to stop)`
+
+```java
+//Assume an array with variable name array is declared before
+for (int i = 0; i < array.length; i++) {
+  // This code will loop through every entry in the array
+}
+```
+
+Note that you don't always have to start from zero, you can start anywhere from the array.
+
+## For Loops + Arrays + Methods
+
+This is an example of how you can take in an array in a method
+
+```java
+public static boolean isEven(int[] array) { // <-- Note the int[] array
+  for (int i = 0; i < array.length; i++) { // Iterate through the entire array
+    // If you find an odd number, return false
+    if (array[i] % 2 == 1) {
+      return false;
+    }
+  }
+  // If you didn't find any odd numbers, return true
+  return true;
+}
+```
+
+## File I/O
+
+Let's say that you have the following file
+
+```
+4
+chicken
+3
+salad
+```
+
+And you want to make it so that you take the number, and print the word after it a certain number of times. For this example we would want to see the following
+
+```java
+chicken chicken chicken chicken
+salad salad salad
+```
+
+Here is the code to write it
+
+```java
+public static void printStrings() {
+  FileInputStream file = new FileInputStream("stuff.txt"); // File contents are in stuff.txt
+  Scanner scnr = new Scanner(file); // Scanner takes in a file to read
+  while (scnr.hasNext()) { // While there are still stuff in the file to read
+  	int number = scnr.nextInt(); // Grab the number
+    String word = scnr.next(); // Grab the word after the number
+    // Print the word number times
+    for (int i = 0; i < number; i++) {
+      System.out.print(word); 
+    }
+    // Put a new line here
+    System.out.println();
+  }
+  
+}
+```
+
+## Recursion
+
+Look at handout and carefully trace recursion problems
+
+## 2D Arrays
+
+Declare a 2D int array with 4 rows and 7 columns
+
+```java
+int[][] dataVals = new int[4][7];
+```
+
+A 2D array with 4 rows and 7 columns has 7 * 4 = 28 entries.
+
+
+
+If you want to sum up all the numbers in a 2 dimensional array, do the following
+
+``` java
+// Assume numbers is declared beforehand
+int sum = 0;
+for (int i = 0; i < numbers.length; i++) { // Loop through every row in the 2D array
+  for (int j = 0; j < numbers[i].length; j++) { // Loop through every column in a row
+    // This code now looks at one entry in a 2D array
+    sum += numbers[i][j];
+  }
+}
+```
+