Done!

src/ArrayPractice.java

@@ -1,18 +1,27 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
-
+    String[] ofFour = new String[4];
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+    ofFour[0] = "Hello";
+    ofFour[1] = "goodbye";
+    ofFour[2] = "Hello Again";
+    ofFour[3] = "Good Night";
 
     // Get the value of the array at index 2
 
+    System.out.println(ofFour[2]);
     // Get the length of the array
-
+    System.out.println(ofFour.length);
     // Iterate over the array using a traditional for loop and print out each item
-
+    for (int i = 0; i < ofFour.length; i++) {
+      System.out.println(ofFour[i]);
+    }
     // Iterate over the array using a for-each loop and print out each item
-
+    for (String string : ofFour) {
+      System.out.println(string);
+    }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,40 @@
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+
 public class ListPractice {
 
 
   public static void main(String[] args) {
     // Create an empty ArrayList of Strings and assign it to a variable of type List
-
+    ArrayList arraylist = new ArrayList();
     // Add 3 elements to the list (OK to do one-by-one)
-
+    arraylist.add("Yo");
+    arraylist.add("Yo2");
+    arraylist.add("Yo3");
+
     // Print the element at index 1
-
+    System.out.println(arraylist.get(1));
     // Replace the element at index 1 with a new value
     // (Do not insert a new value. The length of the list should not change)
-
+    arraylist.set(1, "New Value");
+    System.out.println(arraylist.get(1));
     // Insert a new element at index 0 (the length of the list will change)
-
+    arraylist.add(0, "New 0 index Element");
     // Check whether the list contains a certain string
-
+    arraylist.contains("String");
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
-
+    for (int i = 0; i < arraylist.size(); i++) {
+      System.out.println(arraylist.get(i));
+    }
     // Sort the list using the Collections library
-
+    Collections.sort(arraylist);
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+    for (Object item : arraylist) {
+      System.out.println(item);
+    }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,29 +1,36 @@
-
+import java.util.HashMap;
 
 public class MapPractice {
   public static void main(String[] args) {
     // Create a HashMap with String keys and Integer values and
     // assign it to a variable of type Map
 
+    HashMap<String, Integer> hmp = new HashMap<String, Integer>();
+
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    hmp.put("Number 1", 0);
+    hmp.put("Number 2", 1);
+    hmp.put("Number 3", 2);
 
     // Get the value associated with a given key in the Map
-
+    hmp.get("Number 1");
     // Find the size (number of key/value pairs) of the Map
-
+    System.out.println(hmp.size());
     // Replace the value associated with a given key (the size of the Map shoukld not change)
-
+    hmp.replace("Number 1", 00000);
     // Check whether the Map contains a given key
-
+    hmp.containsKey("Number 4");
     // Check whether the Map contains a given value
-
+    hmp.containsValue(3); 
     // Iterate over the keys of the Map, printing each key
+     //Iterate over the values of the map, printing each value
+         // Iterate over the entries in the map, printing each key and value
 
-    // Iterate over the values of the map, printing each value
-
-    // Iterate over the entries in the map, printing each key and value
-
+    for (String key : hmp.keySet()) {
+      Integer value = hmp.get(key);
+      System.out.println("Key: " + key + ", Value: " + value);
+  }
     /*
      * Usage tip!
      * 

src/NumberPractice.java

@@ -1,18 +1,22 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
-
+    double negativeValue = -4.0; 
     // Create an int with a positive value and assign it to a variable
-
+    int positveValue = 4;
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+    double remainder = positveValue % 3;
     // Use the modulo % operator to determine whether the number is even
     // (A number is even if it has a remainder of zero when divided by 2)
+    if (remainder % 2 == 0) {
+      System.out.println("the Number is even");
+    }
+    else {System.out.println("Number is odd");}
     // Use an if-else to print "Even" if the number is even and "Odd"
     // if the number is odd.
 
     // Divide the number by another number using integer division
-
+    int dividiedInts = 7/7;
     /*
      * Reminder!
      * 

src/Person.java

@@ -7,13 +7,22 @@ public class Person {
   // Declare a public String instance variable for the name of the person
   // Declare a private int instance variable for the age of the person
 
+  public String name;
+  private int age;
 
   // Create a constructor that takes the name and age of the person
   // and assigns it to the instance variables
-
+  public Person (String name, int age) {
+    this.name = name;
+    this.age = age;
+  }
 
   // Create a toString method that gives the name and age of the person
+  public String toString() {
+
 
+    return "This persons name is " + name + " and the age is " + age; 
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -28,26 +37,32 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
+  public int birthYear(int currentYear) {
+    return currentYear - this.age;
+}
 
 
   public static void main(String[] args) {
     // Create an instance of Person
-
+    Person person1 = new Person("Liban James", 44);    
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person person2 = new Person("Bial", 323);
+
 
     // Print the first person
+    person1.toString();
 
     // Print the second person
-
+    person2.toString();
     // Get the name of the first person and store it in a local variable
-
+    String p1Name = person1.name;
     // Using the birthYear method, get the birth year of the first person
     // and store it in a local variable. Input the actual current year (e.g. 2025)
     // as the argument.
-
+    int p1By = person1.birthYear(2025);
     // In a separate statement, print the local variable holding the birth year.
-
+    System.out.println(p1By);
     /**
      * Terminology!
      * 

src/SetPractice.java

@@ -1,18 +1,27 @@
+import java.util.HashSet;
+
 public class SetPractice {
   public static void main(String[] args) {
     // Create a HashSet of Strings and assign it to a variable of type Set
-
+    HashSet<String> hashsetString = new HashSet<>();
+
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
 
+    hashsetString.add("Hello");
+    hashsetString.add("Hello Again");
+    hashsetString.add("Hello Again #2");
     // Check whether the Set contains a given String
+    hashsetString.contains("String"); 
 
     // Remove an element from the Set
-
+    hashsetString.remove("Hello");
     // Get the size of the Set
-
+    System.out.println(hashsetString.size());
     // Iterate over the elements of the Set, printing each one on a separate line
-
+    for (String item : hashsetString) {
+      System.out.println(item);
+    }
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,26 +1,44 @@
+import java.util.ArrayList;
+
 public class StringPractice {
   public static void main(String[] args) {
     // Create a string with at least 5 characters and assign it to a variable
-
+    String five = "ontwo";
     // Find the length of the string
-
+    System.out.println(five.length());
     // Concatenate (add) two strings together and reassign the result
+    String secondString = "another";
 
+    five += secondString;
     // Find the value of the character at index 3
-
+    System.out.println(five.charAt(3));
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
-
+    boolean check = five.contains("abc");
+    System.out.println(check);
     // Iterate over the characters of the string, printing each one on a separate line
-
+    for (int i = 0; i < five.length() ; i++) {
+      System.out.println(five.charAt(i));
+    }
     // Create an ArrayList of Strings and assign it to a variable
-
+    ArrayList newAList = new ArrayList<>();
+
     // Add multiple strings to the List (OK to do one-by-one)
+    newAList.add("Hello");
+    newAList.add("No");
+    newAList.add("Back");
+    newAList.add("Afhasiuhs");
 
     // Join all of the strings in the list together into a single string separated by commas
     // Use a built-in method to achieve this instead of using a loop
+    StringBuilder newString = new StringBuilder();
 
+    for (Object word : newAList) {
+      newString.append(word);
+    }
+    System.out.println(newString);
     // Check whether two strings are equal
-
+    boolean checker = five.equals(secondString);
+    System.out.println(checker);
     /*
      * Reminder!
      * 

toRefresh.md

@@ -2,4 +2,10 @@
 
 As you work through this exercise, write down anything that you needed to look up or struggled to remember here. It can be just a word or two (e.g. "joining strings"). You can use this as a guide of what to make extra sure you're refreshed on before exams and interviews.
 
-- 
+- How to make an array list
+- How to print a element in a arraylist 
+- How to add a new value (arrayList)
+- How to reset a value (arrayList)
+- How to make a hashset (also what is a hashset)
+- How to iterate through hashmap 
+- How to make a constructor