Units 6-10 Review Vocabulary and More!

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Scores of All Homework Assignments Units 6-10!

Unit 6: 0.9/1

Unit 7: 0.8/1

Unit 8: 0.9/1

Unit 9: 0.7/1

Unit 10: 0.8/1

Unit 6

• Array is a type of data structure which contains a collection of data
• Different thant ArrayLists
• Data in arrya can be primitive or referrenced
• Int, float, char, vs String, array, class
• Lowercase for primitive, uppercase for referenced
• Element is value in a box of array, index is position of box, array length is total length of array

How to declare an array -Examples:

• int[] array dom = new int [9]; (saying array length) or int[] array dom = {1,2,3,4,5}

//Unit 6 code example (for and enhanced for loop)
int [] values = {2,5,1};
int total = 0;

for(int i = 0; i < values.length; i++) { //adding values of an array through a for loop
   total += values[i];
}

for(int element : values) { //adding values of an array through an enhanced for loop
   total += element;
}

Unit 7

• ArrayLists are like arrays, but can have vsize changed
• many methods which can be used with arrayLists
• size();
• Returns the number of elements in the list
• add(obj);
• Adds element at the end
• add(index, object);
• Adds element at specific index
• remove(index);
• Removes element from specific index
• set(index, object);
• Replaces element at index with new object
• get(index);
• Returns element at index
• can traverse arrayList with for-loop/enhanced for-loop

// Unit 7 code example
import java.util.ArrayList; //never forget to import

public class methodsArrayList {
    public static void main (String[] args) {
        ArrayList<String> dogs = new ArrayList<String>(Arrays.asList("Sparky", "Duke", "Noodle")); //remeber the <(Variable Type)>
        ArrayList<String> dogs2 = new ArrayList<String>(Arrays.asList("Sparky", "Duke", "Noodle"));
        System.out.println("There are " + dogs.size() + " in the ArrayList"); 
        System.out.println("There are " + dogs2.size() + " in the ArrayList");
        
        //objects you add must be of the same data type
        dogs.add("Peanut"); //using arrayList functions
        System.out.println("There are now " + dogs.size() + " dogs in the ArrayList"); 

        String myDog = dogs.get(2);
        System.out.println("My dog is named " + myDog);
    }
}

//Note: you don't need to declare <String> again after new ArrayList

methodsArrayList.main(null);

Unit 8

// Unit 8 code example
public class Test {

    public static void main(String[] args) {
  
        String[][] arr = { // two indexes, to help store data in a 2D model
            { "Atlanta", "Baltimore", "Chicago" },
            { "Australia", "Boston", "Cincinnati" },
            { "Austin", "Beaumont", "Columbus" }
        };

        String longest = arr[0][0]; //defining the longest array at the moment

        for(int row = 0; row < arr.length; row++) { //incrementing through each part to find largest string
            for(int column = 0; column < arr[row].length; column++) {
                if (arr[row][column].length() > longest.length()) {
                    longest = arr[row][column];
                }
            }
         }

        System.out.println(longest); 

        // Use nested for loops to find the longest or shortest string!
        System.out.println("Use nested for loops to find the longest or shortest string!");
        
    }

 }
Test.main(null);

• 2D Arrays are a lot like arrays, but have an extra index which makes them 2D instead of 1D

Unit 9

• Inheritance is the order in which different attributes, methods, or strings are called
• depends on whentheer class is extended or not, if class contains methods, parameters, strings, etc
• constructor: Where the attributes of a class are defined
• Overriding: allows a subclass or child class to provide a specific implementation of a method that has already been provided by a super-classes or parent classes. When a method in a subclass has the same name, same parameters or signature, and same return type (or sub-type) as a method in its super-class, then the method in the subclass will override the method in the super-class.
• Polymorphism: running mutliple things at once with the same name, can be done with different amounts of parameters in method
• toString method defines and JSONify's data protected is an access modifier so that the attribute isn't affected by outside modifiers.
• to use constructor of superclass in subclass, need to use super keyword, allowing use of constructors that were made in the superclass

// Demonstration of equals method
// Outputs boolean value of true or false
// If one object equals another
public class Student
{
   private String name;

   public Student(String name)
   {
      this.name = name;
   }

   public static void main(String[] args)
   {
      Student student1 = new Student("Bob");
      Student student2 = new Student("Jeff");
      Student student3 = student1;
      Student student4 = new Student("A");
      Student student5 = student4;
      System.out.println(student1.equals(student2));
      System.out.println(student2.equals(student3));
      System.out.println(student1.equals(student3));
      System.out.println(student3.equals(student4));
      System.out.println(student3.equals(student4));
      System.out.println(student5.equals(student4));


   }
}
Student.main(null);

Unit 10

• Recursion is when a method calls itself repeatedly to solve a problem
• Contain two parts
• base case: condition to be reached or returned when conditions are met
• recursive call: the method being run over and over again
• uses if and else statement mainly
• Binary seach algorithm:
• Data has to be in sorted order
• Splits array in half multiple times until value is found
• Selection Sort:
• finds minimum element from unsorted part and puts it at end of sorted part
• Merge Sort:
• splits array into 2, calls it self into two sorted halves, and then merges all the havles back into arrayList

// Unit 10 recursion example
public int fact(int n) // a random number inputed, factorial of which wil be calculated
{
    if (n == 1) // base case 
        return 1; //once n is found to be the same value as 1, the code stops
    else    
        return n*fact(n-1); //if values not equal, then the function keeps calling the else part   
}