Derust

src/ArrayPractice.java

@@ -1,18 +1,28 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
-
+    String[] num = 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
+    num[0] = "kaalid";
+    num[1] = "john";
+    num[2] = "tyler";
+    num[3] = "liban";
 
     // Get the value of the array at index 2
-
+    System.out.println(num[1].toString());
     // Get the length of the array
-
+    System.out.println(num.length);
     // Iterate over the array using a traditional for loop and print out each item
-
+    System.out.println();
+    for(int i = 0; i < num.length; i++) {
+      System.out.println(num[i]);
+    }
     // Iterate over the array using a for-each loop and print out each item
-
+    System.out.println();
+    for(String n : num) {
+      System.out.println(n);
+    }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,40 @@
+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
-
+    ArrayList<String> arr = new ArrayList<>();
     // Add 3 elements to the list (OK to do one-by-one)
-
+    arr.add("john");
+    arr.add("kaalid");
+    arr.add("tyler");
     // Print the element at index 1
-
+    System.out.println(arr.get(0));
     // Replace the element at index 1 with a new value
     // (Do not insert a new value. The length of the list should not change)
-
+    arr.set(0,"david");
+    System.out.println(arr.get(0));
     // Insert a new element at index 0 (the length of the list will change)
-
+    arr.add(0, "liban");
+    System.out.println(arr.get(0));
     // Check whether the list contains a certain string
-
+    System.out.println(arr.contains("david"));
+    System.out.println();
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
-
+    for(int i = 0; i < arr.size(); i++) {
+      System.out.println(arr.get(i));
+    }
     // Sort the list using the Collections library
-
+    Collections.sort(arr);
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+    System.out.println();
+    for(int i = 0; i < arr.size(); i++) {
+      System.out.println(arr.get(i));
+    }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,28 +1,54 @@
+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> map = new HashMap<>();
 
     // Put 3 different key/value pairs in the Map
-    // (it's OK to do this one-by-one)
+    map.put("Apples", 5);
+    map.put("Bananas", 10);
+    map.put("Oranges", 7);
 
     // Get the value associated with a given key in the Map
+    int applesCount = map.get("Apples");
+    System.out.println("Value associated with key 'Apples': " + applesCount);
 
     // Find the size (number of key/value pairs) of the Map
+    int mapSize = map.size();
+    System.out.println("Size of the Map: " + mapSize);
 
-    // 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)
+    map.put("Apples", 8);
+    System.out.println("Updated value for 'Apples': " + map.get("Apples"));
 
     // Check whether the Map contains a given key
+    boolean containsKey = map.containsKey("Bananas");
+    System.out.println("Map contains key 'Bananas': " + containsKey);
 
     // Check whether the Map contains a given value
+    boolean containsValue = map.containsValue(10);
+    System.out.println("Map contains value 10: " + containsValue);
 
     // Iterate over the keys of the Map, printing each key
+    System.out.println("Keys in the Map:");
+    for (String key : map.keySet()) {
+        System.out.println(key);
+    }
 
-    // Iterate over the values of the map, printing each value
+    // Iterate over the values of the Map, printing each value
+    System.out.println("Values in the Map:");
+    for (int value : map.values()) {
+        System.out.println(value);
+    }
 
-    // Iterate over the entries in the map, printing each key and value
+    // Iterate over the entries in the Map, printing each key and value
+    System.out.println("Entries in the Map:");
+    for (Map.Entry<String, Integer> entry : map.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 = -12.34f;
+    System.out.println("Negative float: " + negativeFloat);
 
     // Create an int with a positive value and assign it to a variable
+    int positiveInt = 25;
+    System.out.println("Positive int: " + positiveInt);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    int remainderWhenDividedBy3 = positiveInt % 3;
+    System.out.println("Remainder when " + positiveInt + " is divided by 3: " + remainderWhenDividedBy3);
 
     // 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(positiveInt + " is Even");
+    } else {
+        System.out.println(positiveInt + " is Odd");
+    }
 
     // Divide the number by another number using integer division
+    int divisor = 4;
+    int result = positiveInt / divisor;
+    System.out.println("Result of integer division (" + positiveInt + " / " + divisor + "): " + result);
 
     /*
      * Reminder!

src/Person.java

@@ -3,17 +3,30 @@
  * the Person class.
  */
 
-public class Person {
+/*
+ * In this file you will follow the comments' instructions to complete
+ * the Person class.
+ */
+
+ 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;
 
+  // Declare a private int instance variable for the age of the person
+  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: " + name + ", Age: " + age;
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -27,26 +40,34 @@ 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 person1 = new Person("Alice", 30);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person person2 = new Person("Bob", 25);
 
     // Print the first person
+    System.out.println(person1);
 
     // Print the second person
+    System.out.println(person2);
 
     // Get the name of the first person and store it in a local variable
+    String person1Name = 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 person1BirthYear = person1.birthYear(2025);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println("Birth year of " + person1Name + ": " + person1BirthYear);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,37 @@
+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
+     // Create a HashSet of Strings and assign it to a variable of type Set
+        HashSet<String> stringSet = new HashSet<String>();
 
-    // Add 3 elements to the set
-    // (It's OK to do it one-by-one)
+        // Add 3 elements to the set
+        stringSet.add("Apple");
+        stringSet.add("Banana");
+        stringSet.add("Cherry");
 
-    // Check whether the Set contains a given String
+        // Check whether the Set contains a given String
+        String checkElement = "Banana";
+        if (stringSet.contains(checkElement)) {
+            System.out.println("The set contains: " + checkElement);
+        } else {
+            System.out.println("The set does not contain: " + checkElement);
+        }
 
-    // Remove an element from the Set
+        // Remove an element from the Set
+        stringSet.remove("Apple");
+        System.out.println("After removal " + stringSet);
 
-    // Get the size of the Set
+        // Get the size of the Set
+        int setSize = stringSet.size();
+        System.out.println("Size of the set: " + setSize);
 
-    // Iterate over the elements of the Set, printing each one on a separate line
+        // Iterate over the elements of the Set, printing each one on a separate line
+        System.out.println("Elements in the set:");
+        for (String element : stringSet) {
+            System.out.println(element);
+        }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,25 +1,55 @@
+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
-
-    // Find the length of the string
-
-    // Concatenate (add) two strings together and reassign the result
-
-    // Find the value of the character at index 3
-
-    // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
-
-    // Iterate over the characters of the string, printing each one on a separate line
-
-    // Create an ArrayList of Strings and assign it to a variable
-
-    // Add multiple strings to the List (OK to do one-by-one)
-
-    // 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
-
-    // Check whether two strings are equal
+        String myString = "HelloWorld";
+
+        // Find the length of the string
+        int length = myString.length();
+        System.out.println("Length of the string: " + length);
+
+        // Concatenate (add) two strings together and reassign the result
+        myString = myString + " Java";
+        System.out.println("Concatenated string: " + myString);
+
+        // Find the value of the character at index 3
+        char charAtIndex3 = myString.charAt(3);
+        System.out.println("Character at index 3: " + charAtIndex3);
+
+        // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+        String substring = "abc";
+        boolean containsSubstring = myString.contains(substring);
+        System.out.println("Does the string contain \"" + substring + "\"? " + containsSubstring);
+
+        // Iterate over the characters of the string, printing each one on a separate line
+        System.out.println("Characters in the string:");
+        for (char c : myString.toCharArray()) {
+            System.out.println(c);
+        }
+
+        // Create an ArrayList of Strings and assign it to a variable
+        List<String> stringList = new ArrayList<>();
+
+        // Add multiple strings to the List (OK to do one-by-one)
+        stringList.add("Apple");
+        stringList.add("Banana");
+        stringList.add("Cherry");
+
+        // 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 joinedString = String.join(", ", stringList);
+        System.out.println("Joined string: " + joinedString);
+
+        // Check whether two strings are equal
+        String string1 = "Hello";
+        String string2 = "hello";
+        boolean areEqual = string1.equals(string2); // Case-sensitive comparison
+        boolean areEqualIgnoreCase = string1.equalsIgnoreCase(string2); // Case-insensitive comparison
+        System.out.println("Are the strings equal (case-sensitive)? " + areEqual);
+        System.out.println("Are the strings equal (case-insensitive)? " + areEqualIgnoreCase);
+
 
     /*
      * Reminder!