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