Java Derusting Completion.

src/ArrayPractice.java

@@ -1,17 +1,30 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
+    String[] strings = 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
+    strings[0] = "Hello";
+    strings[1] = "What's up!";
+    strings[2] = "Greetings.";
+    strings[3] = "Howdy!";
 
     // Get the value of the array at index 2
+    System.out.println(strings[2]);
 
     // Get the length of the array
+    System.out.println(strings.length);
 
     // Iterate over the array using a traditional for loop and print out each item
+    for (int i = 0; i < strings.length; i++) {
+      System.out.println(strings[i]);
+    }
 
     // Iterate over the array using a for-each loop and print out each item
+    for (String x : strings) {
+      System.out.println(x);
+    }
 
     /*
      * Reminder!

src/ListPractice.java

@@ -1,27 +1,46 @@
-public class ListPractice {
+import java.util.ArrayList;
+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<String> myStrings = new ArrayList<>();
 
     // Add 3 elements to the list (OK to do one-by-one)
+    myStrings.add("I love dogs!");
+    myStrings.add("Hey there.");
+    myStrings.add("Avengers, assemble.");
 
     // Print the element at index 1
+    System.out.println(myStrings.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)
+    myStrings.set(1, "Woah, I'm different!");
 
     // Insert a new element at index 0 (the length of the list will change)
+    myStrings.addFirst("New guy here...");
 
     // Check whether the list contains a certain string
+    // EXPECTED: TRUE
+    System.out.println("Contains new guy?: " + myStrings.contains("New guy here..."));
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for (int i = 0; i < myStrings.size(); i++) {
+      System.out.println("[" + myStrings.get(i) + "]" + " at " + "index " + i);
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(myStrings);
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    System.out.println();
+    for (String x : myStrings) {
+      System.out.println(x);
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,28 +1,47 @@
-
+import java.util.HashMap;
+import java.util.Map;
 
 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
+    Map<String, Integer> myMap = new HashMap<>(); 
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    myMap.put("One", 1);
+    myMap.put("Two", 2);
+    myMap.put("Three", 3);
 
     // Get the value associated with a given key in the Map
+    System.out.println(myMap.get("One"));
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(myMap.size());
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+    myMap.replace("One", 0);
 
     // Check whether the Map contains a given key
+    System.out.println("Contains Key One: " + myMap.containsKey("One"));
 
     // Check whether the Map contains a given value
+    System.out.println("Contains Value 1: " + myMap.containsValue(1));
 
     // Iterate over the keys of the Map, printing each key
+    for (String key : myMap.keySet()) {
+      System.out.println(key);
+    }
 
     // Iterate over the values of the map, printing each value
+    for (int value : myMap.values()) {
+      System.out.println(value);
+    }
 
     // Iterate over the entries in the map, printing each key and value
+    for (Map.Entry<String, Integer> entry : myMap.entrySet()) {
+      System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue());
+    }
 
     /*
      * Usage tip!

src/NumberPractice.java

@@ -1,17 +1,29 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
+    float negativeFloat = -1.0f;
+    System.out.println("Negative Float Value: " + negativeFloat);
 
     // Create an int with a positive value and assign it to a variable
+    int positiveInt = 15;
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    int remainder = (positiveInt % 3);
+    System.out.println("Remainder: " + remainder);
 
     // 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)
     // Use an if-else to print "Even" if the number is even and "Odd"
     // if the number is odd.
-
+    if ((positiveInt % 2) == 0) {
+      System.out.println("Even!");
+    } else {
+      System.out.println("Odd!");
+    }
+
     // Divide the number by another number using integer division
+    int dividedNum = positiveInt / 5;
+    System.out.println("Integer Division: " + dividedNum);
 
     /*
      * Reminder!

src/Person.java

@@ -6,13 +6,22 @@
 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
+  @Override
+  public String toString () {
+    return name + " " + age;
+  }
 
 
   // Implement the below public instance method "birthYear"
@@ -28,25 +37,35 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
+  public int birthYear (int currentYear) {
+    return currentYear - age;
+  } 
 
 
   public static void main(String[] args) {
     // Create an instance of Person
+    Person me = new Person("Ahmed", 18);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person friend = new Person("Amelia", 20);
 
     // Print the first person
+    System.out.println(me.name);
 
     // Print the second person
+    System.out.println(friend.name);
 
     // Get the name of the first person and store it in a local variable
+    String myName = me.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 myYear = me.birthYear(2025);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(myYear);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,30 @@
+import java.util.HashSet;
+import java.util.Set;
+
 public class SetPractice {
   public static void main(String[] args) {
     // Create a HashSet of Strings and assign it to a variable of type Set
+    Set<String> myStrings = new HashSet<>();
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    myStrings.add("One");
+    myStrings.add("Two");
+    myStrings.add("Three");
 
     // Check whether the Set contains a given String
+    System.out.println(myStrings.contains("Two"));
 
     // Remove an element from the Set
+    myStrings.remove("Three");
 
     // Get the size of the Set
+    System.out.println(myStrings.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
+    for (String x : myStrings) {
+      System.out.println(x);
+    }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,25 +1,42 @@
+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 myString = "Ahmed";
 
     // Find the length of the string
+    System.out.println("String Length: " + myString.length());
 
     // Concatenate (add) two strings together and reassign the result
+    myString = (myString + "Heythere!");
 
     // Find the value of the character at index 3
+    System.out.println("Value at index three: " + myString.charAt(3));
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    System.out.println("Contains Ahm?: " + myString.contains("Ahm"));
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < myString.length(); i++) {
+      System.out.println(myString.charAt(i));
+    }
 
     // Create an ArrayList of Strings and assign it to a variable
+    ArrayList<String> myArray = new ArrayList<>();
 
     // Add multiple strings to the List (OK to do one-by-one)
+    myArray.add("Wuzzup");
+    myArray.add("Hello yo!");
+    myArray.add("I like cheese.");
 
     // 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
+    String test = String.join(", ", myArray);
+    System.out.println(test);
 
     // Check whether two strings are equal
+    System.out.println("They equal?: " + myArray.get(0).equals(myArray.get(1)));
 
     /*
      * Reminder!