Completed Practices

src/ArrayPractice.java

@@ -1,17 +1,33 @@
+import java.util.*;
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
+    String[] arrayExample = new String[4];
+    System.out.println(Arrays.toString(arrayExample));
 
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+    arrayExample[0] = "Hello";
+    arrayExample[1] = "To";
+    arrayExample[2] = "Java";
+    arrayExample[3] = "Derusting";
+    System.out.println(Arrays.toString(arrayExample));
 
     // Get the value of the array at index 2
+    System.out.println(arrayExample[2]);
 
     // Get the length of the array
+    System.out.println(arrayExample.length);
 
     // Iterate over the array using a traditional for loop and print out each item
+    for (int i = 0; i < arrayExample.length; i++) {
+      System.out.println(arrayExample[i]);
+    }
 
     // Iterate over the array using a for-each loop and print out each item
+    for (String word : arrayExample) {
+      System.out.println(word);
+    }
 
     /*
      * Reminder!

src/ListPractice.java

@@ -1,27 +1,51 @@
+import java.util.*;
+
 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> listExample = new ArrayList<>();
+    System.out.println(listExample);
 
     // Add 3 elements to the list (OK to do one-by-one)
+    listExample.add("Hello");
+    listExample.add("Java");
+    listExample.add("Derusting");
+    System.out.println(listExample);
 
     // Print the element at index 1
+    System.out.println(listExample.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)
+    listExample.set(1, "ArrayList");
+    System.out.println(listExample);
 
     // Insert a new element at index 0 (the length of the list will change)
+    listExample.add(0, "Assignment:");
+    System.out.println(listExample);
 
     // Check whether the list contains a certain string
+    if (listExample.contains("Hello")) {
+      System.out.println("Yes! It has the element Hello");
+    }
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for (int i = 0; i < listExample.size(); i++) {
+      System.out.println(i + "=" + listExample.get(i));
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(listExample);
+    System.out.println(listExample);
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    for (String word : listExample) {
+      System.out.println(word);
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,28 +1,53 @@
-
+import java.util.*;
 
 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> mapExample = new HashMap<>();
+    System.out.println(mapExample);
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    mapExample.put("Twix", 2);
+    mapExample.put("Milky Way", 3);
+    mapExample.put("Crunch", 4);
+    System.out.println(mapExample);
 
     // Get the value associated with a given key in the Map
+    System.out.println(mapExample.get("Twix"));
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(mapExample.size());
 
-    // 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)
+    mapExample.put("Twix", 5);
+    System.out.println(mapExample);
 
     // Check whether the Map contains a given key
+    if (mapExample.containsKey("Twix")) {
+      System.out.println("Yes! It contains the key Twix");
+    }
 
     // Check whether the Map contains a given value
+    if (mapExample.containsValue(5)) {
+      System.out.println("Yes! It contains the value 5");
+    }
 
     // Iterate over the keys of the Map, printing each key
+    for (String key : mapExample.keySet()) {
+      System.out.println(key);
+    }
 
     // Iterate over the values of the map, printing each value
+    for (Integer value : mapExample.values()) {
+      System.out.println(value);
+    }
 
     // Iterate over the entries in the map, printing each key and value
+    for (Map.Entry<String, Integer> entry : mapExample.entrySet()) {
+      System.out.println(entry.getKey() + ":" + 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 floatNum = -3.5f;
+    System.out.println(floatNum);
 
     // Create an int with a positive value and assign it to a variable
+    int intNum = 3;
+    System.out.println(intNum);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    System.out.println("The remainder of the int is: " + intNum % 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 (intNum % 2 == 0) {
+      System.out.println("Even");
+    }
+    else {
+      System.out.println("Odd");
+    }
 
     // Divide the number by another number using integer division
+    System.out.println(intNum / 2);
 
     /*
      * 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 personName;
+  private int personAge;
 
   // Create a constructor that takes the name and age of the person
   // and assigns it to the instance variables
-
+  public Person(String personName, int personAge) {
+    this.personName = personName;
+    this.personAge = personAge;
+  }
 
   // Create a toString method that gives the name and age of the person
-
+  @Override
+  public String toString() {
+    return "Name: " + personName + " Age: " + personAge;
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -28,25 +35,36 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
-
+  public int birthYear(int currentYear) {
+    int birthYear = currentYear - personAge;
+    return birthYear;
+  }
 
   public static void main(String[] args) {
     // Create an instance of Person
+    Person xavier = new Person("Xavier", 20);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person sera = new Person("Sera", 22);
 
     // Print the first person
+    System.out.println(xavier);
 
     // Print the second person
+    System.out.println(sera);
 
     // Get the name of the first person and store it in a local variable
+    String firstName = xavier.personName;
+    System.out.println(firstName);
 
     // 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 firstBirthYear = xavier.birthYear(2025);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(firstBirthYear);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,34 @@
+import java.util.*;
+
 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> setExample = new HashSet<>();
+    System.out.println(setExample);
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    setExample.add("Hello");
+    setExample.add("Set");
+    setExample.add("Practice");
+    System.out.println(setExample);
 
     // Check whether the Set contains a given String
+    if (setExample.contains("Hello")) {
+      System.out.println("Yes! It does contain Hello");
+    }
 
     // Remove an element from the Set
+    setExample.remove("Hello");
+    System.out.println(setExample);
 
     // Get the size of the Set
+    System.out.println(setExample.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
+    for (String word : setExample) {
+      System.out.println(word);
+    }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,25 +1,52 @@
+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 word = "Hello";
+    System.out.println(word);
+
     // Find the length of the string
+    System.out.println(word.length());
 
     // Concatenate (add) two strings together and reassign the result
+    word = word + " World";
+    System.out.println(word);
 
     // Find the value of the character at index 3
+    System.out.println(word.charAt(3));
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    if (word.contains("Hel")) {
+      System.out.println("Yes! The word contains the substring");
+    }
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < word.length(); i++) {
+      System.out.println(word.charAt(i));
+    }
 
     // Create an ArrayList of Strings and assign it to a variable
+    ArrayList<String> stringList = new ArrayList<>();
+    System.out.println(stringList);
 
     // Add multiple strings to the List (OK to do one-by-one)
+    stringList.add("Hello");
+    stringList.add("String");
+    stringList.add("Practice");
+    System.out.println(stringList);
 
     // 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));
 
     // Check whether two strings are equal
+    if (stringList.get(0).equals(stringList.get(1))) {
+      System.out.println("Yes they are the same!");
+    }
+    else {
+      System.out.println("No they are different!");
+    }
 
     /*
      * Reminder!