mirror of
https://github.com/Brandon-Rozek/website.git
synced 2024-11-09 18:50:34 -05:00
125 lines
2.9 KiB
Markdown
125 lines
2.9 KiB
Markdown
# 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];
|
|
}
|
|
}
|
|
```
|
|
|