Completed Java Derusting Assignment

src/ArrayPractice.java

@@ -1,17 +1,31 @@
 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] = "Freedom";
+    strings[1] = "Duty";
+    strings[2] = "Loner";
+    strings[3] = "Monolith";
 
     // Get the value of the array at index 2
+    System.out.println(strings[2] + "\n");
 
     // Get the length of the array
+    System.out.println(strings.length + "\n");
 
     // 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]);
+    }
+    System.out.println("\n");
 
     // Iterate over the array using a for-each loop and print out each item
+    for (String string : strings) {
+      System.out.println(string);
+    }
 
     /*
      * Reminder!

src/ListPractice.java

@@ -1,27 +1,52 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 public class ListPractice {
 
 
   public static void main(String[] args) {
     // Create an empty ArrayList of Strings and assign it to a variable of type List
+    List<String> stringList = new ArrayList<String>();
 
     // Add 3 elements to the list (OK to do one-by-one)
+    stringList.add("Hello");
+    stringList.add("Hi");
+    stringList.add("Greetings");
+    System.out.println(stringList + "\n");
 
     // Print the element at index 1
+    System.out.println(stringList.get(1) + "\n");
 
     // Replace the element at index 1 with a new value
     // (Do not insert a new value. The length of the list should not change)
+    stringList.set(1, "Salutations");
+    System.out.println(stringList + "\n");
 
     // Insert a new element at index 0 (the length of the list will change)
+    stringList.add(0, "Blessings");
+    System.out.println(stringList + "\n");
 
     // Check whether the list contains a certain string
+    if (stringList.contains("Greetings")) {
+      System.out.println("I greet thee as well." + "\n");
+    }
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for(int i = 0; i < stringList.size(); i++) {
+      System.out.println(stringList.get(i) + "\n");
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(stringList);
+    System.out.println("List is sorted." + "\n");
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    for(String word : stringList) {
+      System.out.println(word + "\n");
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,28 +1,51 @@
-
+import java.util.Map;
+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
+    Map<String, Integer> hashMap = new HashMap<String, Integer>();
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
-
+    hashMap.put("Monolith", 1);
+    hashMap.put("Freedom", 2);
+    hashMap.put("Duty", 3);
+    System.out.println(hashMap + "\n");
+
     // Get the value associated with a given key in the Map
+    System.out.println(hashMap.get("Monolith") + "\n");
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(hashMap.size() + "\n");
 
-    // Replace the value associated with a given key (the size of the Map shoukld not change)
+    // Replace the value associated with a given key (the size of the Map should not change)
+    hashMap.put("Monolith", 4);
+    System.out.println(hashMap + "\n");
 
     // Check whether the Map contains a given key
+    System.out.println(hashMap.containsKey("Freedom") + "\n");
 
     // Check whether the Map contains a given value
+    System.out.println(hashMap.containsValue(4) + "\n");
 
     // Iterate over the keys of the Map, printing each key
+    for (String key : hashMap.keySet()) {
+      System.out.println(key);
+    }
+    System.out.println("\n");
 
     // Iterate over the values of the map, printing each value
+    for (Integer value : hashMap.values()) {
+      System.out.println(value);
+    }
+    System.out.println("\n");
 
     // Iterate over the entries in the map, printing each key and value
+    for (String key : hashMap.keySet()) {
+      System.out.println(key + ", " + hashMap.get(key));
+    }
 
     /*
      * Usage tip!

src/NumberPractice.java

@@ -1,18 +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 f = -3.6f;
+    System.out.println(f);
 
     // Create an int with a positive value and assign it to a variable
+    int i = 4;
+    System.out.println(i);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    System.out.println(i % 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)
     // Use an if-else to print "Even" if the number is even and "Odd"
     // if the number is odd.
+    if (i % 2 == 0) {
+      System.out.println("Even");
+    } else {
+      System.out.println("Odd");
+    }
 
     // Divide the number by another number using integer division
 
+    System.out.println(i / 4);
     /*
      * Reminder!
      * 

src/Person.java

@@ -6,14 +6,21 @@
 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 "This person is called " + name + ", they are " + age + " years old.";
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -27,26 +34,35 @@ public class Person {
    * @param currentYear an int for the current year
    * @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 John = new Person("John", 22);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person Smith = new Person("Smith", 53);
 
     // Print the first person
+    System.out.println(John.toString());
 
     // Print the second person
+    System.out.println(Smith.toString());
 
     // Get the name of the first person and store it in a local variable
+    String firstName = John.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 firstBirth = John.birthYear(2025);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(firstName + " was born in " + firstBirth + ".");
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,31 @@
+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> hashSet = new HashSet<String>();
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    hashSet.add("Monolith");
+    hashSet.add("Freedom");
+    hashSet.add("Duty");
+    System.out.println(hashSet + "\n");
 
     // Check whether the Set contains a given String
+    System.out.println(hashSet.contains("Freedom") + "\n");
 
     // Remove an element from the Set
+    hashSet.remove("Freedom");
 
     // Get the size of the Set
+    System.out.println(hashSet.size() + "\n");
 
     // Iterate over the elements of the Set, printing each one on a separate line
+    for (String string : hashSet) {
+      System.out.println(string);
+    }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,25 +1,51 @@
+import java.util.ArrayList;
+import java.util.List;
+
 public class StringPractice {
   public static void main(String[] args) {
     // Create a string with at least 5 characters and assign it to a variable
+    String string = "Monolith";
+    System.out.println(string + "\n");
 
     // Find the length of the string
+    System.out.println(string.length() + "\n");
 
     // Concatenate (add) two strings together and reassign the result
+    String add = " Emissary";
+    string = string + add;
+    System.out.println(string + "\n");
 
     // Find the value of the character at index 3
+    System.out.println(string.charAt(3) + "\n");
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    System.out.println(string.contains("Mon") + "\n");
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < string.length(); i++) {
+      System.out.println(string.charAt(i));
+    }
+    System.out.println("\n");
 
     // Create an ArrayList of Strings and assign it to a variable
+    List<String> stringList = new ArrayList<String>();
 
     // Add multiple strings to the List (OK to do one-by-one)
+    stringList.add("Monolith");
+    stringList.add("Freedom");
+    stringList.add("Fighter");
+    System.out.println(stringList + "\n");
 
     // 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
+    System.out.println(String.join(", ", stringList) + "\n");
 
     // Check whether two strings are equal
+    if (string.equals(add)) {
+      System.out.println("The strings are equal.");
+    } else {
+      System.out.println("The strings are not equal.");
+    }
 
     /*
      * Reminder!

toRefresh.md

@@ -2,4 +2,9 @@
 
 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.
 
-- 
+- floating integers
+- instantiating ArrayLists
+- for each loops
+- joining strings
+- printing key along with value in a single loop
+- the entire Person.java class