SDEV333 Java Derusting homework PR

src/ArrayPractice.java

@@ -1,18 +1,25 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
-
+    String[] stringArray = 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
-
+    stringArray[0] = "apple";
+    stringArray[1] = "banana";
+    stringArray[2] = "date";
+    stringArray[3] = "cherry";
     // Get the value of the array at index 2
-
+    System.out.println(stringArray[2]);
     // Get the length of the array
-
+    System.out.println(stringArray.length);
     // Iterate over the array using a traditional for loop and print out each item
-
+    for (int i = 0; i < stringArray.length; i++) {
+      System.out.println(stringArray[i]);
+    }
     // Iterate over the array using a for-each loop and print out each item
-
+    for (String element : stringArray) {
+      System.out.println(element);
+    }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,27 +1,42 @@
+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> aList = new ArrayList<>();
     // Add 3 elements to the list (OK to do one-by-one)
-
+    aList.add("apple");
+    aList.add("orange");
+    aList.add("banana");
     // Print the element at index 1
-
+    System.out.println(aList.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)
-
+    aList.set(1, "cumquat");
     // Insert a new element at index 0 (the length of the list will change)
-
+    aList.add(0, "grapes");
     // Check whether the list contains a certain string
-
+    if (aList.contains("avocado")) {
+      System.out.println("The list contains 'avocado'.");
+    } else {
+      System.out.println("The list does not contain 'avocado'.");
+    }
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
-
+    for (int i = 0; i < aList.size(); i++) {
+      System.out.println("Index: " + i + ", Value: " + aList.get(i));
+    }
     // Sort the list using the Collections library
-
+    Collections.sort(aList);
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    for (String element : aList) {
+      System.out.println(element);
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,29 +1,42 @@
-
+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
-
+    Map<String, Integer> mappy = new HashMap<>();
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
-
+    mappy.put("kitties", 3);
+    mappy.put("doggies", 4);
+    mappy.put("fishies", 11);
     // Get the value associated with a given key in the Map
-
+    System.out.println(mappy.get("fishies"));
     // Find the size (number of key/value pairs) of the Map
-
+    System.out.println(mappy.size());
     // Replace the value associated with a given key (the size of the Map shoukld not change)
-
+    mappy.replace("kitties", 5);
     // Check whether the Map contains a given key
-
+    boolean qKey = mappy.containsKey("doggies");
+    System.out.println(qKey);
     // Check whether the Map contains a given value
-
+    boolean qValue = mappy.containsValue(2);
+    System.out.println(qValue);
     // Iterate over the keys of the Map, printing each key
-
+    for (String elementKey : mappy.keySet()) {
+      System.out.println(elementKey);
+    }
     // Iterate over the values of the map, printing each value
-
+    for (Integer elementValue : mappy.values()) {
+      System.out.println(elementValue);
+    }
     // Iterate over the entries in the map, printing each key and value
-
+    // Map.Entry<String, Integer> entry I had to ask for help from chatGPT on this part
+    for (Map.Entry<String, Integer> entry : mappy.entrySet()) {
+      System.out.println("Key: " + entry.getKey() + ", Value: " +
+      entry.getValue());
+    }
     /*
      * Usage tip!
      * 

src/NumberPractice.java

@@ -1,17 +1,22 @@
 public class NumberPractice {
-  public static void main(String args[]) {
+  public static void main(String[] args) {
     // Create a float with a negative value and assign it to a variable
-
+    float floater = -7.77f;
     // Create an int with a positive value and assign it to a variable
-
+    int winter = 12;
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+    int modRemain = winter % 3;
+    System.out.println("Remainder when divided by 3: " + modRemain);
     // 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 (winter % 2 == 0) {System.out.println("Even");} 
+      else {System.out.println("Odd");}
     // Divide the number by another number using integer division
+    int newResult = winter / 5; // Example: divide winter by 5
+    System.out.println("Integer division result: " + newResult);
+
 
     /*
      * Reminder!
@@ -23,3 +28,4 @@ public static void main(String args[]) {
 
   }
 }
+

src/Person.java

@@ -5,15 +5,22 @@
 
 public class Person {
   // Declare a public String instance variable for the name 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.
@@ -28,26 +35,29 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
+  public int birthYear(int currentYear) {
+    return currentYear - this.age;
+  }
 
 
   public static void main(String[] args) {
     // Create an instance of Person
-
+    Person steveH = new Person("Steve Hardy", 32);
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
-
+    Person sallieR = new Person("Sallie Ride", 49);
     // Print the first person
-
+    System.out.println(steveH);
     // Print the second person
-
+    System.out.println(sallieR);
     // Get the name of the first person and store it in a local variable
-
+    String firstName = steveH.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 birthYearSteve = steveH.birthYear(2025);
     // In a separate statement, print the local variable holding the birth year.
-
+    System.out.println("Birth year of " + firstName + ": " + birthYearSteve);
     /**
      * Terminology!
      * 

src/SetPractice.java

@@ -1,18 +1,26 @@
+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> hashy = new HashSet<>();
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
-
+    hashy.add("metal");
+    hashy.add("water");
+    hashy.add("air");
     // Check whether the Set contains a given String
-
+    boolean doesIt = hashy.contains("air");
+    System.out.println(doesIt);
     // Remove an element from the Set
-
+    hashy.remove("air");
     // Get the size of the Set
-
+    System.out.println(hashy.size());
     // Iterate over the elements of the Set, printing each one on a separate line
-
+    for (String element : hashy) {
+      System.out.println(element);
+    }
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,26 +1,39 @@
+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 stringy = "apple";
     // Find the length of the string
-
+    System.out.println(stringy.length());
     // Concatenate (add) two strings together and reassign the result
-
+    String kitty = "cinder" + "block";
     // Find the value of the character at index 3
-
+    System.out.println(kitty.charAt(3));
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
-
+    boolean sub = kitty.contains("abc");
+    System.out.println(sub);
     // Iterate over the characters of the string, printing each one on a separate line
-
+    for (int i = 0; i < kitty.length(); i++) {
+      System.out.println(kitty.charAt(i));
+    }
     // Create an ArrayList of Strings and assign it to a variable
-
+    ArrayList<String> listy = new ArrayList<>();
     // Add multiple strings to the List (OK to do one-by-one)
+    listy.add("kitty");
+    listy.add("doggy");
+    listy.add("birdy");
+    listy.add("horsy");
+    listy.add("piggy");
+    listy.add("donkey");
+    listy.add("cow");
 
     // 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 joined = String.join(",", listy);
     // Check whether two strings are equal
-
+    boolean equal = kitty.equals(joined);
+    System.out.println(equal);
     /*
      * Reminder!
      * 

toRefresh.md

@@ -2,4 +2,12 @@
 
 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.
 
-- 
+- Taken from MapPractice.java class: 
+// Iterate over the entries in the map, printing each key and value
+    // Map.Entry<String, Integer> entry I had to ask for help from chatGPT on this part
+    for (Map.Entry<String, Integer> entry : mappy.entrySet()) {
+      System.out.println("Key: " + entry.getKey() + ", Value: " +
+      entry.getValue());
+    }
+
+-