Finish the practice

src/ArrayPractice.java

@@ -1,22 +1,33 @@
+
+
 public class ArrayPractice {
   public static void main(String[] args) {
-    // Create an array of Strings of size 4
+      // Create an array of Strings of size 4
+      String[] fruits = 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
+      // Set the value of the array at each index to be a different String
+      fruits[0] = "Apple";
+      fruits[1] = "Banana";
+      fruits[2] = "Cherry";
+      fruits[3] = "Date";
 
-    // Get the value of the array at index 2
+      // Get the value of the array at index 2
+      System.out.println("Element at index 2: " + fruits[2]); // Expected: Cherry
 
-    // Get the length of the array
+      // Get the length of the array
+      System.out.println("Length of the array: " + fruits.length); // Expected: 4
 
-    // Iterate over the array using a traditional for loop and print out each item
+      // Iterate over the array using a traditional for loop and print out each item
+      System.out.println("Using traditional for loop:");
+      for (int i = 0; i < fruits.length; i++) {
+          System.out.println(fruits[i]); // Prints each fruit
+      }
 
-    // Iterate over the array using a for-each loop and print out each item
-
-    /*
-     * Reminder!
-     * 
-     * Arrays start at index 0
-     */
+      // Iterate over the array using a for-each loop and print out each item
+      System.out.println("Using for-each loop:");
+      for (String fruit : fruits) {
+          System.out.println(fruit); // Prints each fruit
+      }
   }
 }
+

src/ListPractice.java

@@ -1,36 +1,48 @@
+import java.util.ArrayList;
+import java.util.List;
+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
-
-    // Add 3 elements to the list (OK to do one-by-one)
-
-    // Print the element at index 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)
-
-    // Insert a new element at index 0 (the length of the list will change)
-
-    // Check whether the list contains a certain string
-
-    // Iterate over the list using a traditional for-loop.
-    // Print each index and value on a separate line
-
-    // Sort the list using the Collections library
-
-    // Iterate over the list using a for-each loop
-    // Print each value on a second line
-
-    /*
-     * Usage tip!
-     * 
-     * Use a traditional for-loop when you need to use the index or you need to iterate in an
-     * unconventional order (e.g. backwards)
-     * 
-     * Otherwise, if you're iterating the in the conventional order and don't need the
-     * index values a for-each loop is cleaner.
-     */
-  }
-}
+    public static void main(String[] args) {
+        // Create an empty ArrayList of Strings and assign it to a variable of type List
+        List<String> myList = new ArrayList<>();
+
+        // Add 3 elements to the list (OK to do one-by-one)
+        myList.add("Apple");
+        myList.add("Banana");
+        myList.add("Cherry");
+
+        // Print the element at index 1
+        System.out.println("Element at index 1: " + myList.get(1)); // Expected: Banana
+
+        // Replace the element at index 1 with a new value
+        myList.set(1, "Grapes"); // Replaces "Banana" with "Grapes"
+        System.out.println("List after replacement: " + myList); // Expected: [Apple, Grapes, Cherry]
+
+        // Insert a new element at index 0 (the length of the list will change)
+        myList.add(0, "Orange"); // Inserts "Orange" at the beginning
+        System.out.println("List after insertion: " + myList); // Expected: [Orange, Apple, Grapes, Cherry]
+
+        // Check whether the list contains a certain string
+        boolean containsApple = myList.contains("Apple");
+        System.out.println("Does the list contain 'Apple'? " + containsApple); // Expected: true
+
+        // Iterate over the list using a traditional for-loop.
+        // Print each index and value on a separate line
+        System.out.println("Using traditional for-loop:");
+        for (int i = 0; i < myList.size(); i++) {
+            System.out.println("Index " + i + ": " + myList.get(i)); // Prints index and value
+        }
+
+        // Sort the list using the Collections library
+        Collections.sort(myList); // Sorts the list alphabetically
+        System.out.println("List after sorting: " + myList); // Expected: [Apple, Cherry, Grapes, Orange]
+
+        // Iterate over the list using a for-each loop
+        // Print each value on a second line
+        System.out.println("Using for-each loop:");
+        for (String item : myList) {
+            System.out.println(item); // Prints each value on a new line
+        }
+    }
+}

src/MapPractice.java

@@ -1,28 +1,58 @@
-
+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
 
-    // Put 3 different key/value pairs in the Map
-    // (it's OK to do this one-by-one)
+    // Method to create and return a Map
+    public static Map<String, Integer> createMap() {
+        Map<String, Integer> ages = new HashMap<>();
+        ages.put("Elena", 27);
+        ages.put("Demon", 30);
+        ages.put("Shams", 23);
+        return ages;
+    }
+
+    public static void main(String[] args) {
+        // Create the map and populate it
+        Map<String, Integer> myMap = createMap();
+
+        // Get the value associated with a given key in the Map
+        System.out.println("Age of Elena: " + myMap.get("Elena"));
+
+        // Find the size (number of key/value pairs) of the Map
+        System.out.println("Size of the map: " + myMap.size()); 
+        // Replace the value associated with a given key
+        myMap.put("Demon", 31); // Changing Demon’s age to 31
+        System.out.println("Updated map: " + myMap); 
 
-    // Get the value associated with a given key in the Map
+        // Check whether the Map contains a given key
+        System.out.println("Does the map contain 'Shams'? " + myMap.containsKey("Shams"));
 
-    // Find the size (number of key/value pairs) of the Map
+        // Check whether the Map contains a given value
+        System.out.println("Does the map contain the value 30? " + myMap.containsValue(30)); 
 
-    // Replace the value associated with a given key (the size of the Map shoukld not change)
+        // Iterate over the keys of the Map, printing each key
+        System.out.println("Keys in the map:");
+        for (String key : myMap.keySet()) {
+            System.out.println(key); 
+        }
 
-    // Check whether the Map contains a given key
+        // Iterate over the values of the map, printing each value
+        System.out.println("Values in the map:");
+        for (Integer value : myMap.values()) {
+            System.out.println(value); 
+        }
 
-    // Check whether the Map contains a given value
+        // Iterate over the entries in the map, printing each key and value
+        System.out.println("Entries in the map (key and value):");
+        for (Map.Entry<String, Integer> entry : myMap.entrySet()) {
+            System.out.println(entry.getKey() + ": " + entry.getValue()); 
+        }
+
+
 
-    // 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
 
     /*
      * Usage tip!

src/NumberPractice.java

@@ -1,25 +1,34 @@
 public class NumberPractice {
   public static void main(String args[]) {
-    // Create a float with a negative value and assign it to a variable
+      // Create a float with a negative value and assign it to a variable
+      float negativeFloat = -5.7f;
+      System.out.println("Negative float value: " + negativeFloat); // Using the variable
 
-    // Create an int with a positive value and assign it to a variable
+      // Create an int with a positive value and assign it to a variable
+      int positiveInt = 10;
 
-    // Use the modulo % operator to find the remainder when the int is divided by 3
+      // Use the modulo % operator to find the remainder when the int is divided by 3
+      int remainder = positiveInt % 3;
+      System.out.println("Remainder when " + positiveInt + " is divided by 3: " + 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.
+      // 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 (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
-
-    /*
-     * Reminder!
-     * 
-     * When dividing ints, the result is rounded down.
-     * Example: 
-     * 7 / 3 = 2 when performing int division
-     */
+      // Divide the number by another number using integer division
+      int result = positiveInt / 3;
+      System.out.println("Result of integer division of " + positiveInt + " by 3: " + result);
 
+      /*
+       * Reminder!
+       * 
+       * When dividing ints, the result is rounded down.
+       * Example: 
+       * 7 / 3 = 2 when performing int division
+       */
   }
 }

src/Person.java

@@ -1,66 +1,76 @@
-/*
- * 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;
 
-  // Create a constructor that takes the name and age of the person
-  // and assigns it to the instance variables
+  // 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() {
+      // This method returns a string that represents the Person object with their name and age
+      return name + " (" + age + " years old)";
+  }
 
-
-  // Implement the below public instance method "birthYear"
-  // There should NOT be any print statement in this method.
+  // Implement the public instance method "birthYear"
+  // This method returns the year the person was born
   /**
    * birthYear returns the year the person was born.
    * 
-   * The birth year is calculated by subtracting the person's age from currentYear
+   * The birth year is calculated by subtracting the person's age from the currentYear
    * that's passed in as an int. It assumes that the person's birthday has already
    * passed this year.
    * 
    * @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) {
+      // Calculate the birth year by subtracting the person's age from the current year
+      return currentYear - age;
+  }
 
   public static void main(String[] args) {
-    // Create an instance of Person
-
-    // Create another instance of Person with a different name and age and
-    // assign it to a different variable
-
-    // Print the first person
-
-    // Print the second person
-
-    // Get the name of the first person and store it in a local variable
-
-    // 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.
-
-    // In a separate statement, print the local variable holding the birth year.
-
-    /**
-     * Terminology!
-     * 
-     * A class is the overall definition, like a blueprint.
-     * An instance is a specific object made according to that definition.
-     * We use "instance" and "object" to mean the same thing.
-     * 
-     * For example, if there is a Person class, we can make an instance of a specific person: Auberon.
-     * 
-     * There can be many instances for the same class. For example: Auberon, Xinting, Baya are all
-     * different instances of the Person class.
-     * 
-     * Each instance has its own instance variables: Auberon's age can be different from Baya's age.
-     */
-  }
-}
+      // Create an instance of Person with the name "Elena" and age 27
+      Person person1 = new Person("Elena", 27);
+
+      // Create another instance of Person with a different name and age
+      Person person2 = new Person("Demon", 30);
+
+      // Print the first person (calls toString method)
+      System.out.println(person1); // This will print: Elena (27 years old)
+
+      // Print the second person (calls toString method)
+      System.out.println(person2); // This will print: John (30 years old)
+
+      // Get the name of the first person and store it in a local variable
+      String personName = person1.name; // personName will be "Elena"
+
+      // Using the birthYear method, get the birth year of the first person
+      // and store it in a local variable. Input the current year (e.g., 2025) as the argument.
+      int birthYearOfPerson1 = person1.birthYear(2025);
+
+      // In a separate statement, print the local variable holding the birth year.
+      System.out.println(personName + "'s birth year: " + birthYearOfPerson1); // This will print: Elena's birth year: 1998
+
+      /**
+       * Terminology!
+       * 
+       * A class is the overall definition, like a blueprint.
+       * An instance is a specific object made according to that definition.
+       * We use "instance" and "object" to mean the same thing.
+       * 
+       * For example, if there is a Person class, we can make an instance of a specific person: Auberon.
+       * 
+       * There can be many instances for the same class. For example: Auberon, Xinting, Baya are all
+       * different instances of the Person class.
+       * 
+       * Each instance has its own instance variables: Auberon's age can be different from Baya's age.
+       */
+  } 
+}