Derusting Pull Request

src/ArrayPractice.java

@@ -1,18 +1,34 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
-
+      String[] stringArr = 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
-
+      stringArr[0] = "Github";
+      stringArr[1] = "Gitlab";
+      stringArr[2] = "Gitea";
+      stringArr[3] = "Bitbucket";
     // Get the value of the array at index 2
-
+      String indexThree = stringArr[2];
+      System.out.println(indexThree);
+      System.out.println();
     // Get the length of the array
+      int arrLen = stringArr.length;
+      System.out.println(arrLen);
+
+      System.out.println();
 
     // Iterate over the array using a traditional for loop and print out each item
+      for (int i = 0; i < stringArr.length; i++) {
+        System.out.println(stringArr[i]);
+
+      }
+      System.out.println();
 
     // Iterate over the array using a for-each loop and print out each item
-
+      for (String item : stringArr) {
+        System.out.println(item);
+      }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,42 @@
+import java.util.List;
+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
-
+      List<String> stringList = new ArrayList<>();
     // Add 3 elements to the list (OK to do one-by-one)
-
+      stringList.add("Singapore");
+      stringList.add("Seoul");
+      stringList.add("Shanghai");
     // Print the element at index 1
-
+      stringList.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)
-
+      stringList.set(1, "Sapporo");
     // Insert a new element at index 0 (the length of the list will change)
-
+      stringList.add(1, "Singapore");
+      System.out.println(stringList);
     // Check whether the list contains a certain string
-
+      Boolean containsCity = stringList.contains("Seoul");
+      System.out.println(containsCity);
     // 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(i + " " + stringList.get(i) + " ");
+      }
     // Sort the list using the Collections library
-
+        Collections.sort(stringList);
+        System.out.println(stringList);
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+        for (String item : stringList) {
+          System.out.println(item);
+        }
+      }
     /*
      * Usage tip!
      * 
@@ -33,4 +47,3 @@ public static void main(String[] args) {
      * index values a for-each loop is cleaner.
      */
   }
-}

src/MapPractice.java

@@ -1,28 +1,52 @@
-
+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> map = new HashMap();
+
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    map.put("Mercury", 1);
+    map.put("Venus", 2);
+    map.put("Mars", 3);
 
     // Get the value associated with a given key in the Map
+    Integer closestPlanet = map.get("Mercury");
+    System.out.println(closestPlanet);
 
     // Find the size (number of key/value pairs) of the Map
-
+    int numOfPlanets = map.size();
+    System.out.println(numOfPlanets);
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+
+    map.replace("Mars", 4);
+    Integer ourPlanet = map.get("Mars");
+    System.out.println(ourPlanet);
+    int newNumOfPlanets = map.size();
+    System.out.println(newNumOfPlanets);
 
     // Check whether the Map contains a given key
+    boolean hasMars = map.containsKey("Mars"); 
+    System.out.println(hasMars);
 
     // Check whether the Map contains a given value
-
+    boolean hasFive = map.containsValue(5);
+    System.out.println(hasFive);
     // Iterate over the keys of the Map, printing each key
-
+    for (Map.Entry<String, Integer> entry : map.entrySet()) {
+      System.out.println(entry.getKey());
+  }
     // Iterate over the values of the map, printing each value
-
+    for (Map.Entry<String, Integer> entry : map.entrySet()) {
+      System.out.println(entry.getValue());
+  }
     // Iterate over the entries in the map, printing each key and value
+    for (Map.Entry<String, Integer> entry : map.entrySet()) {
+      System.out.println("Key: " + entry.getKey() + " Value: " + entry.getValue());
+  }
 
     /*
      * Usage tip!

src/NumberPractice.java

@@ -1,25 +1,54 @@
 public class NumberPractice {
-  public static void main(String args[]) {
-    // Create a float with a negative value and assign it to a variable
+    public static void main(String args[]) {
 
-    // Create an int with a positive value and assign it to a variable
-
-    // Use the modulo % operator to find the remainder when the int is divided by 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.
+        // Create a float with a negative value and assign it to a variable
+        float negativeFloatVal = -5.75f;
+        System.out.println(negativeFloatVal);
+
+        // Create an int with a positive value and assign it to a variable
+        int positiveIntVal = 88;
+        System.out.println(positiveIntVal);
+
+        // Use the modulo % operator to find the remainder when the int is divided by 3
+        int divisibleByThree = positiveIntVal % 3;
+        System.out.println(divisibleByThree);
+
+        // 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.
+        int[] numsArray = {1, 2, 3, 4, 5, 6};
+        evenOrOdd(numsArray);
+
+        int numOne = 9; 
+        int numTwo = 4;
+        int dividedNumber = divideNumber(numOne, numTwo);
+        System.out.println(dividedNumber);
+    }
 
+    public static void evenOrOdd(int[] numsArray) {
+        for (int i = 0; i < numsArray.length; i++) {
+            if (numsArray[i] % 2 == 0) {
+                System.out.println("Even");
+            } else {
+                System.out.println("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
      */
-
-  }
-}
+    public static int divideNumber(int numOne, int numTwo) {
+        if (numOne == 0 || numTwo == 0) {
+            return 0;
+        }
+        int result = numOne / numTwo;
+        return result;
+    }
+}

src/Person.java

@@ -6,14 +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: " + name + ", Age: " + age; 
+    }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -29,24 +37,37 @@ public class Person {
    */
   // (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 Bob = new Person("Bob", 61);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person Tommy = new Person("Tommy", 5);
 
     // Print the first person
+    System.out.println(Bob);
 
     // Print the second person
+    System.out.println(Tommy);
 
     // Get the name of the first person and store it in a local variable
-
+    String name = Bob.name;
+    System.out.println(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 AgeOfBob = Bob.birthYear(2025);
+
 
     // In a separate statement, print the local variable holding the birth year.
+      System.out.println(AgeOfBob);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,27 @@
+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> fruits = new HashSet<>();     
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
-
+      fruits.add("kiwis");
+      fruits.add("cherries");
+      fruits.add("blueberries");
     // Check whether the Set contains a given String
-
+      boolean isAFruit = fruits.contains("blueberries");
+      System.out.println(isAFruit);
     // Remove an element from the Set
+      fruits.remove("blueberries");    
 
     // Get the size of the Set
-
+      System.out.println(fruits.size());
     // Iterate over the elements of the Set, printing each one on a separate line
+    for (String fruit : fruits) {
+      System.out.println(fruit);
+    }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,26 +1,55 @@
+import java.util.List;
+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 keyboardCharsCaps = "WASD";
 
     // Find the length of the string
+    int lengthOfKeyboardChars = keyboardCharsCaps.length();
+    System.out.println(lengthOfKeyboardChars);
 
     // Concatenate (add) two strings together and reassign the result
+    String part1 = "Postgres";
+    String part2 = "SQL";
+
+    String complete = part1 + part2;
+
+    System.out.println(complete);
 
     // Find the value of the character at index 3
+    char ch = complete.charAt(3);
+    System.out.println(ch);
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    boolean hasABC = complete.contains("abc");
+    System.out.println(hasABC);
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < complete.length(); i++) {
+      System.out.println(complete.charAt(i));
+    }
 
     // Create an ArrayList of Strings and assign it to a variable
+    List<String> list = new ArrayList<>();
 
     // Add multiple strings to the List (OK to do one-by-one)
+    list.add("Jupiter");
+    list.add("Saturn");
+    list.add("Neptune");
 
+    System.out.println(list);
     // 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 planetsList = String.join(", ", list);    
+      System.out.println(planetsList);
+      // Check whether two strings are equal
+      String string1 = "Python";
+      String string2 = "C++";
+      boolean areEqual = string1.equals(string2);
+      System.out.println(areEqual);
+
     /*
      * Reminder!
      *